JP4997961B2 - Integrated duplexer - Google Patents

Description

  The present invention belongs to the technical field of communication equipment, and relates to a thin film piezoelectric resonator and a thin film piezoelectric filter using the same.

  The RF circuit part of a cellular telephone is always required to be downsized. Recently, it has been demanded to add various functions to cellular phones, and it is preferable to incorporate as many components as possible in order to realize them, while the size of cellular phones is limited. Therefore, there is a strict demand for reduction of the exclusive area (mounting area) and height in the equipment, and therefore, components constituting the RF circuit portion are required to have a small exclusive area and a low height.

  Under such circumstances, surface acoustic wave filters and thin film piezoelectric filters that are small and can be reduced in weight are used as band-pass filters used in RF circuits. In particular, in the high frequency band of 2 GHz or more, many thin film piezoelectric filters having excellent electrical characteristics are used. The thin film piezoelectric filter as described above forms a piezoelectric thin film such as aluminum nitride (AlN) or zinc oxide (ZnO) so as to be sandwiched between upper and lower electrodes on the substrate, and elastic wave energy does not leak into the semiconductor substrate. Thus, the RF filter is formed of a thin film piezoelectric resonator in which a vibration space or an acoustic reflection layer is provided immediately below.

  On the other hand, recent cellular telephones are equipped with a plurality of RF circuits so that they can be applied to various communication systems. Therefore, it is necessary to separate signal components having different frequency bands, and a method for switching signals using a semiconductor switch or the like is generally used as the means. However, it is necessary to separate AMPS (824 MHz-894 MHz band), PCS (1850-1990 MHz band), and GPS (1574 MHz-1576 MHz band) from the correspondence to the E911 system in the United States, In recent years, a triplexer that does not use an active element such as a semiconductor switch has been used due to the miniaturization of equipment.

  As a form of a triplexer that does not use a semiconductor switch or the like, as shown in Patent Document 1 and Patent Document 2, it is composed of an LC filter composed of an inductor and a capacitor, and the LC filter is composed of a laminated body composed of ceramics or resin. There is a duplexer. Further, as shown in Patent Document 3, Patent Document 4, and Non-Patent Document 1, the LC filter is composed of a combination of an LC filter composed of an inductor and a capacitor and a SAW filter, and the LC filter is formed on a multilayer substrate composed of ceramic or resin, There is a duplexer in which a SAW filter is mounted on a laminated substrate.

  As shown in Patent Document 1 and Patent Document 2, when a duplexer such as a triplexer is formed by a filter element formed in a ceramic multilayer substrate, the size of the ceramic multilayer substrate is reduced due to restrictions in the manufacturing process of the ceramic multilayer substrate. There are limits. Furthermore, since many electrical elements are formed in the multilayer substrate, it is difficult to reduce the height. In addition, the AMPS, GPS, and PCS triplexers require that the GPS circuit has a large out-of-band attenuation, so that when the LC filter is formed, a sufficient out-of-band attenuation cannot be ensured. There was a problem.

  As shown in Patent Document 3, Patent Document 4, and Non-Patent Document 1, in a duplexer in which a filter element formed in a ceramic multilayer substrate and a SAW filter are combined, a process for forming the ceramic multilayer substrate is performed. There is a limit to downsizing due to restrictions. FIG. 9 is a schematic cross-sectional view showing the duplexer shown in Patent Document 3, Patent Document 4, and Non-Patent Document 1. A SAW filter 140 and an inductor / capacitor chip component 150 are mounted on a package 130 formed of a multilayer substrate, and an LC filter including a capacitor portion 131 and an inductor portion 132 is formed in the multilayer substrate. As apparent from FIG. 9, since many electric elements are formed in the multilayer substrate, it is difficult to reduce the height, and the SAW filter has a low quality factor in the high frequency band of 1 GHz or more and insertion loss. There is a problem that becomes larger.

  As described above, in recent years, in order to add various functions to cellular telephones, RF parts are required to be downsized, and modularization of a plurality of parts as one is rapidly progressing. As a duplexer to be incorporated in a module, the occupied area is small and the height is severely limited. As described in Patent Documents 1 to 4 and Non-Patent Document 1, when a filter element is formed on a multilayer substrate, it is difficult to reduce the thickness of the multilayer substrate, and it is difficult to reduce the height. Therefore, there is a demand for a duplexer that can be reduced in size and height and has good characteristics.

  The present invention has been made in view of the above circumstances, and is an extremely small, low-profile integrated demultiplexer having good characteristics, and a small, high-performance high-frequency demultiplexer. The purpose is to provide a vessel.

JP 2003-8385 A Japanese Patent Laid-Open No. 2003-115736 JP 2004-194240 A JP 2006-108824 A “Design of High Integrated Triplexer Using LTCC Technology”, Proceedings of IEEE MTT Symposium 2006, pp. 199 378-381

The present invention is an integrated duplexer in which a thin film piezoelectric filter composed of a thin film piezoelectric resonator and an integrated filter are formed on a substrate having an insulating layer formed on an upper surface of a semiconductor substrate, and the thickness of the insulating layer Is 5 μm or more, and the material constituting the semiconductor substrate has an electrical resistivity of 1 to 10 [Ω · cm], and the thin film piezoelectric resonator faces the piezoelectric layer with the piezoelectric layer interposed therebetween. A piezoelectric resonance stack having an upper electrode and a lower electrode formed as described above, a void or an acoustic reflection layer formed under the piezoelectric resonance stack, and the substrate supporting the piezoelectric resonance stack, The integrated filter relates to an integrated duplexer that is formed on the insulating layer and includes electrical elements of an inductor and a capacitor.

The present invention also relates to the integrated duplexer, wherein the insulating layer is a silicon oxide layer obtained by thermal oxidation .

The present invention also relates to the integrated duplexer, wherein the fixed charge density in the insulating layer is 1 × 10 ¹¹ cm ⁻² or less.

  The present invention also relates to the integrated duplexer, wherein the integrated filter including the inductor and capacitor electrical elements is a diplexer, and the integrated duplexer is a triplexer.

  Further, according to the present invention, the integrated duplexer is mounted on a package made of a multilayer substrate, and the matching circuit element including at least one of an inductor, a capacitor, and a distributed constant line is formed on the multilayer substrate. The present invention relates to a high-frequency branching filter characterized by that.

  According to the integrated duplexer of the present invention, an integrated duplexer in which a thin film piezoelectric filter composed of a thin film piezoelectric resonator and an integrated filter are formed on a substrate having an insulating layer formed on an upper surface of a semiconductor substrate. The thin film piezoelectric resonator includes a piezoelectric resonance stack having a piezoelectric layer and an upper electrode and a lower electrode formed to face each other with the piezoelectric layer interposed therebetween, and a gap formed under the piezoelectric resonance stack. Alternatively, an integrated duplexer that includes an acoustic reflection layer and the substrate that supports the piezoelectric resonant stack, and the integrated filter is formed on the insulating layer and includes an electrical element of an inductor and a capacitor. By doing so, it is possible to provide an integrated duplexer that is very small and low in profile and that has high performance.

According to the integrated duplexer of the present invention, an integrated duplexer having excellent performance with small insertion loss in the passband and large out-of-band attenuation can be obtained by setting the thickness of the insulating layer to 5 μm or more. In addition, a low-resistance wafer can be used, and the manufacturing cost can be reduced.

According to the integrated duplexer of the present invention, when the fixed charge density in the insulating layer is 1 × 10 ¹¹ cm ⁻² or less, the insertion loss in the passband is small and the out-of-band attenuation is excellent. An integrated duplexer having performance can be provided.

  According to the present invention, the integrated duplexer is mounted on a package made of a multilayer substrate, and a matching circuit comprising at least one of an inductor, a capacitor, and a distributed constant line is formed on the multilayer substrate. Therefore, it is possible to provide a high-performance high-frequency branching filter that is small and low in profile, has a small insertion loss in the passband, and has a large out-of-band attenuation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An object of the present invention is to provide a very small, thin and high performance integrated duplexer and a small and high performance high frequency duplexer.

  FIG. 1 shows a schematic cross-sectional view of an embodiment of an integrated duplexer of the present invention. In the integrated duplexer, a thin film piezoelectric filter 101 made of a thin film piezoelectric resonator and an integrated filter 110 made of electrical elements such as an inductor and a capacitor are formed on a substrate in which an insulating layer 8 is formed on a semiconductor substrate 6. . Examples of the integrated filter include a low pass filter, a high pass filter, and a band pass filter. Furthermore, a duplexer called a diplexer that combines a low-pass filter and a high-pass filter can be formed. The thickness of the insulating layer formed on the semiconductor substrate 6 is preferably 5 μm or more. By setting the thickness of the insulating layer to 5 μm or more, the resonance characteristics of the thin film piezoelectric resonator, in particular, a reduction in impedance at the anti-resonance frequency can be suppressed, and the passive elements constituting the integrated filter, in particular, Loss at high frequency of the inductor can be reduced. More preferably, the thickness of the insulating layer is preferably 5 μm or more and 30 μm or less. In order to suppress a decrease in impedance at the antiresonance frequency of the thin film piezoelectric resonator, an insulating layer thickness of 5 μm or more is necessary. However, forming an insulating layer of 30 μm or more causes an increase in manufacturing cost. Therefore, it is not preferable.

  The thin film piezoelectric resonator includes a piezoelectric resonance stack having a piezoelectric layer and an upper electrode 12 and a lower electrode 10 formed so as to face each other with the piezoelectric layer interposed therebetween, and a gap formed under the piezoelectric resonance stack or An acoustic reflection layer and the substrate supporting the piezoelectric resonance stack are configured. The lower electrode 10, the piezoelectric layer 2, and the upper electrode 12 are sequentially stacked on the vibration space formed in the insulating layer. A plurality of thin film piezoelectric resonators are electrically connected via a connection conductor 14 to constitute a thin film piezoelectric filter. As the configuration and material of the thin film piezoelectric resonator, the semiconductor substrate 6 may be a silicon substrate, a gallium arsenide substrate, a glass substrate, or the like, but a silicon substrate that is inexpensive and capable of increasing the diameter is suitable. Further, when the thickness of the insulating layer is 5 μm or more, a low resistivity semiconductor substrate having a resistivity of less than 1000 [Ω · cm] can be used. A low-resistance silicon substrate having a resistivity of less than 1000 [Ω · cm] is preferable because it is less expensive than a high-resistance silicon substrate and can reduce manufacturing costs. Specifically, a low resistance wafer of about 1 [Ω · cm] to 10 [Ω · cm], which is often used in a normal semiconductor process, can be used. Therefore, the resistivity of the semiconductor substrate used in the present invention can be 1 [Ω · cm] or more and less than 1000 [Ω · cm].

  FIGS. 7A and 7B are circuit diagrams showing an embodiment of a thin film piezoelectric filter constituting the integrated duplexer of the present invention. As shown in FIGS. 7A and 7B, a thin film piezoelectric filter can be configured by connecting a resonator to a ladder type and a lattice type. The ladder filter shown in FIG. 7A has a circuit configuration in which series resonators 102a, 102b, and 102c and parallel resonators 103a, 103b, and 103c are connected in a ladder shape. The parallel resonators 103a, 103b, and 103c are set to have a lower resonance frequency than the series resonators 102a, 102b, and 102c. As shown in the schematic cross-sectional view of FIG. 1, the resonance frequency can be lowered by adding the frequency adjustment layer 16. Also in the lattice filter shown in FIG. 7B, the parallel resonators 103a and 103b are set to have a lower resonance frequency than the series resonators 102a and 102b.

The thin film piezoelectric resonator constituting the integrated duplexer of the present invention can be manufactured, for example, as follows. An insulating layer 8 is formed on a semiconductor substrate 6 such as a silicon wafer by a film formation technique such as sputtering or CVD. When the insulating layer 8 is silicon oxide (SiO ₂ ), the SiO ₂ layer can be formed by thermal oxidation in addition to the above-described film forming technique. The insulating layer 8 is formed by film formation or thermal oxidation so as to have a thickness of 5 μm or more. Thereafter, a sacrificial layer that is easily dissolved by an etching solution is formed by a film formation method such as sputtering or vapor deposition, and patterning is performed using a patterning technique such as wet etching, RIE, or lift-off. As the sacrificial layer, a metal such as germanium (Ge), aluminum (Al), titanium (Ti), magnesium (Mg), or a metal oxide thereof is suitable. Thereafter, the lower electrode 10, the piezoelectric layer 2, and the upper electrode 12 are formed by a film forming method such as sputtering or vapor deposition, and each layer is patterned using a patterning technique such as wet etching, RIE, or lift-off. Further, after forming the through hole 18 reaching from the upper surface of the substrate to the sacrificial layer using the patterning technique, the sacrificial layer is removed with an etching solution. Furthermore, by selecting an etchant that can etch the insulating layer 8 and etching the insulating layer, the insulating layer can be etched in the same pattern as the sacrificial layer. Thereby, the vibration space 4 can be formed in the sacrificial layer and the insulating layer. In addition, the step of etching the sacrificial layer and the insulating layer using an etching solution can be performed after an integrated filter described later is formed. It is preferable to set the vibration space forming process as the final process because damage to the thin film piezoelectric resonator in the manufacturing process can be suppressed.

  The integrated filter constituting the integrated duplexer of the present invention includes a capacitor formed on an insulating layer and an electrical element of an inductor. The material constituting the capacitor portion can be composed of a dielectric thin film such as SiN usually used in a semiconductor process. In addition, it is preferable to use Au or Cu having a low electrical resistivity as a material constituting the inductor portion. In order to suppress loss at high frequency, the thickness of the thin film conductor is set to 5 μm or more, so that loss at higher frequency is achieved. Can be reduced, which is preferable. Further, as the interlayer insulating layer between the wirings and between the layers, an insulator such as BCB (Benzo Cyclo Butene) or polyimide usually used in a semiconductor process can be used.

  The integrated filter which is one embodiment of the present invention shown in FIG. 1 can be manufactured as follows. A dielectric thin film 54 constituting a capacitor is formed on the electrode 52 connected to the lower electrode constituting the thin film piezoelectric resonator via the connection conductor 14 by the above-described film forming method, and the above-described patterning is performed. Patterning into a predetermined shape using a technique. Further, an electrode layer 56 serving as an upper electrode constituting the capacitor structure is formed and patterned into a predetermined shape. Thereafter, a first interlayer insulating layer 58 is formed. An electrode layer 62 for forming an inductor is formed on the first interlayer insulating layer by the film forming method and patterned into a predetermined shape. In order to reduce the loss at high frequency, it is desirable to use a thick film forming technique such as a plating method when an electrode layer of 5 μm or more is formed. Further, a conductor via 64 is formed in the insulating layer 58 and connected to the electrode layer 52. Next, a second interlayer insulating layer 60 is formed, conductor vias 64 are formed in the second interlayer insulating layer, and input / output portions are formed on the device surface layer.

As a method of manufacturing the integrated duplexer of the present invention, after the insulating layer formation step, in a non-oxidizing gas atmosphere (N ₂ , Ar, N ₂ / H ₂ mixed gas, Ar / H ₂ mixed gas, etc.) By performing heat treatment at a temperature of 300 ° C. or higher, ultraviolet irradiation with an irradiation intensity of 100 mW / cm ² or higher, or a combination thereof, the fixed charge density of the insulating layer 8 can be significantly reduced. By setting the fixed charge density to 1 × 10 ¹¹ cm ⁻² or less, it is possible to suppress a decrease in the resonance characteristics of the thin film piezoelectric resonator, particularly the impedance at the anti-resonance frequency, and configure an integrated filter. Loss at a high frequency of a passive element, particularly an inductor can be reduced. The fixed charge density is preferably as small as possible. However, since it is difficult to make the fixed charge density in the insulating layer formed by the conventional technique less than 1 × 10 ⁹ cm ⁻² , the fixed charge density is 1 × 10 ^9. If it is cm ⁻² or more and 1 × 10 ¹¹ cm ⁻² or less, a decrease in impedance at the antiresonance frequency of the thin film piezoelectric resonator can be suppressed.

  FIG. 3 shows one configuration of the high frequency demultiplexer according to the embodiment of the present invention. The duplexer 100 includes a low-pass filter (Low Pass Filter: LPF) 111 made up of LC electric elements, a high-pass filter (High Pass Filter: HPF) 112, and a band-pass filter made up of a thin film piezoelectric filter 101. These components are sealed in the package 130. The package includes a common terminal and first to third terminals. The common terminal is an antenna terminal, the first and third terminals are terminals for inputting and outputting signals in the first and third frequency bands, and the second terminal is a receiving terminal for signals in the second frequency band. Become. The low-pass filter is provided between the common terminal and the first terminal, and the high-pass filter is provided between the common terminal and the third terminal, and the integrated filter 110 shown in FIG. Is formed. Moreover, the band pass filter which consists of the said thin film piezoelectric filter is provided between the common terminal and the 2nd terminal, and is equivalent to the thin film piezoelectric filter part 101 shown in FIG. As described above, the low pass filter, the high pass filter, and the thin film piezoelectric filter are formed on the same substrate. As a result, a duplexer having a small size, a small thickness, and good characteristics is realized.

  FIG. 4 is a schematic sectional view showing an embodiment of the integrated duplexer of the present invention mounted in a package. In the integrated duplexer 100 according to the present invention, a thin film piezoelectric filter portion formed of a thin film piezoelectric resonator and an integrated filter formed of passive elements such as an inductor and a capacitor are formed on the same substrate. The integrated duplexer 100 is mounted in a package 130, and the integrated duplexer is connected to the common terminal of the package 130 and the first to third terminals by a conductor. In FIG. 4, the integrated duplexer is mounted on a flip chip. Flip mounting is preferable because the height can be further reduced.

  FIG. 2 is a schematic cross-sectional view of an embodiment of the integrated duplexer of the present invention different from that in FIG. The integrated duplexer shown in FIG. 2 differs from the embodiment of FIG. 1 in that a thin film piezoelectric resonator comprising a lower electrode 10, a piezoelectric layer 2, and an upper electrode 12 is formed on an acoustic reflection layer 20. Yes. In the embodiment of FIG. 2 as well, a very small, thin, and high-performance integrated duplexer can be realized.

The material constituting the integrated duplexer of FIG. 2 can be manufactured using the same material as the integrated duplexer shown in FIG. The thin film piezoelectric filter 101 constituting the integrated duplexer of FIG. 2 can be manufactured as follows. An insulating layer 8 is formed on a semiconductor substrate 6 such as a silicon substrate by a film forming technique such as sputtering, vapor deposition or CVD, or a thermal oxidation method, and then a pit portion is formed in the insulating layer 8 by a technique such as wet etching. After that, the acoustic reflection layer 20 is formed by the above-described film forming technique. Thereafter, the surface of the substrate is flattened by a flattening technique such as a CMP method to obtain a substrate on which the acoustic reflection layer 20 is deposited only inside the pits. The acoustic reflection layer 20 is preferably a material having a low acoustic impedance such as SiO ₂ or AlN as the low impedance layer, and a material having a large acoustic impedance such as Mo, W, or Ta ₂ O ₅ as the high impedance layer. By setting the thickness of the layer and the high impedance layer so as to correspond to a quarter wavelength of the elastic wave, the layer acts as an acoustic reflection layer. The lower electrode 10, the piezoelectric layer 2, the upper electrode 12, and the frequency adjustment layer 16 are formed by a film formation method such as sputtering or vapor deposition, and each layer is patterned using a patterning technique such as wet etching, RIE, or lift-off method. By doing so, the thin film piezoelectric filter 101 shown in FIG. 2 can be produced. Further, the integrated filter 110 constituting the integrated duplexer of FIG. 2 can be manufactured by the same method as that of FIG.

  The integrated duplexer shown in FIG. 2 can be configured as shown in FIG. 3 in the same manner as the integrated duplexer shown in FIG. That is, the duplexer shown in FIG. 3 is also an embodiment of the integrated duplexer shown in FIG.

  FIG. 5 shows one configuration of the high frequency demultiplexer according to the embodiment of the present invention. The duplexer 100 includes a low-pass filter (LPF) 111, a high-pass filter (HPF) 112 made of an electric element of an inductor and a capacitor, a band-pass filter made of a thin-film piezoelectric filter 101, an inductor, And a matching circuit 120 including at least one of a capacitor and a distributed constant line. These components are sealed in the package 130. The package includes a common terminal and first to third terminals. The common terminal is an antenna terminal, the first and third terminals are terminals for inputting and outputting signals in the first and third frequency bands, and the second terminal is a receiving terminal for signals in the second frequency band. Become. The low-pass filter 111 is provided between the common terminal and the first terminal, and the high-pass filter 112 is provided between the common terminal and the third terminal. The band-pass filter made of the thin film piezoelectric filter is provided between the common terminal and the second terminal, and the matching circuit 120 is arranged between the common terminal and the band-pass filter. The low-pass filter, the high-pass filter, and the thin film piezoelectric filter are formed on the same substrate, and the matching circuit is formed in the package 130.

  The matching circuit prevents a signal passing through the band pass filter 101 from interfering with a signal passing through the low pass filter 111 and the high pass filter 112. Specifically, the matching circuit 120 is configured so that the impedance in the frequency band of the first and third signals passing through the band-pass filter 101 is infinite in the reflection characteristics from the common terminal side. FIG. 8 shows an example of an electric circuit in the case where a matching circuit is constituted by an electric element of an inductor and a capacitor. As shown in FIGS. 8A, 8B, 8C, and 8D, there is a matching circuit in which an inductor and a capacitor are configured in a π type or a T type. Also, it can be configured using a distributed constant line having a characteristic impedance of 50Ω.

  By providing the matching circuit, the insertion loss of each signal passing through the low-pass filter 111, the high-pass filter 112, and the band-pass filter 101 is reduced, and a higher-performance high-frequency demultiplexer can be realized.

  FIG. 6 is a schematic cross-sectional view showing an embodiment of a high frequency demultiplexer according to an embodiment of the present invention. In the integrated duplexer 100 of the present invention, a thin film piezoelectric filter portion 101 composed of a thin film piezoelectric resonator and an integrated filter composed of passive elements such as inductors and capacitors are formed on the same substrate. The integrated duplexer 100 is mounted in the package 130, and the integrated duplexer and the common terminal of the package 130 and the first to third terminals are electrically connected. The matching circuit 120 is formed in the package 130, and it is not necessary to use a chip component such as a chip inductor or a chip capacitor, and a small high-frequency duplexer can be realized. In FIG. 6, the integrated duplexer is mounted on a flip chip. Flip mounting is preferable because the height can be further reduced.

It is a typical sectional view showing one embodiment of an integrated duplexer of the present invention. It is a typical sectional view showing one embodiment of an integrated duplexer of the present invention. It is a block diagram which shows one Embodiment of the high frequency branching filter using the integrated branching filter of this invention. It is a typical sectional view showing one embodiment of a high frequency branching filter using an integrated branching filter of the present invention. It is a block diagram which shows one Embodiment of the high frequency branching filter using the integrated branching filter of this invention. It is a typical sectional view showing one embodiment of a high frequency branching filter using an integrated branching filter of the present invention. It is a circuit diagram of (a) ladder type filter and (b) lattice type filter which show one embodiment of the circuit composition of the thin film piezoelectric filter which constitutes the integrated branching filter of the present invention. It is a circuit diagram of (a) pi type circuit and (b) T type circuit showing one embodiment of a matching circuit which constitutes a high frequency branching filter using an integrated branching filter of the present invention. It is typical sectional drawing which shows one Embodiment of the conventional splitter.

Explanation of symbols

2 Piezoelectric layer 4 Vibration space 6 Semiconductor substrate 8 Insulating layer 10 Lower electrode 12 Upper electrode 14 Connection conductor 16 Frequency adjustment layer 18 Sacrificial layer etching through hole 20 Acoustic reflection layer 52 Capacitor lower electrode 54 Dielectric thin film 56 Capacitor configuration Upper electrode 58 First insulator layer 60 Second insulator layer 62 Inductor forming electrode 64 Conductor via 100 Integrated duplexer 101 Thin film piezoelectric filter 102, 102a-d Series thin film piezoelectric resonator 103, 103a-d Parallel thin film piezoelectric resonance Child 110 Integrated LC filter or integrated LC demultiplexer 111 Low-pass filter 112 High-pass filter 120 Matching circuit 130 Package 131 Capacitor portion formed in multilayer substrate 132 Inductor portion formed in multilayer substrate 140 SAW chip 150 Chip component

Claims (5)

An integrated demultiplexer in which a thin film piezoelectric filter composed of a thin film piezoelectric resonator and an integrated filter are formed on a substrate having an insulating layer formed on an upper surface of a semiconductor substrate,
The insulating layer has a thickness of 5 μm or more,
The material constituting the semiconductor substrate has an electrical resistivity of 1 to 10 [Ω · cm],
The thin film piezoelectric resonator includes a piezoelectric resonance stack having a piezoelectric layer and an upper electrode and a lower electrode formed so as to face each other with the piezoelectric layer interposed therebetween, and a gap or acoustic reflection formed under the piezoelectric resonance stack. An integrated duplexer comprising a layer and the substrate supporting the piezoelectric resonant stack, wherein the integrated filter is formed on the insulating layer and comprises an electrical element of an inductor and a capacitor. 2. The integrated demultiplexer according to claim 1, wherein the insulating layer is a silicon oxide layer obtained by thermal oxidation. 2. The integrated demultiplexer according to claim 1, wherein the fixed charge density in the insulating layer is 1 × 10 ¹¹ cm ⁻² or less.   2. The integrated duplexer according to claim 1, wherein the integrated filter comprising the electric elements of the inductor and the capacitor constitutes a diplexer, and the integrated duplexer is a triplexer.   A high frequency duplexer comprising the integrated duplexer according to claim 1 and a package on which the integrated duplexer is mounted, the package comprising a multilayer substrate, the multilayer substrate comprising an inductor and a capacitor A high frequency branching filter comprising a matching circuit element formed of at least one of distributed constant lines.

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