JPS5856464A - Manufacture of mos semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor element having excellent element characteristics by holding a gate forming region in the state that an impurity of the prescribed density of the same conductive type as a semiconductor substrate is injected. CONSTITUTION:An oxidized film 5 is newly formed by a heat treatment on the surface of a semiconductor substrate 1, windows 8a, 9a are opened at the portions corresponding to regions to be formed with its source 8 and its drain 9, an impurity of reverse conductive type as a semiconductor substrate 1 is introduced, thereby forming a high density source region 8a and a high density drain region 9a. Then, a new oxidized film is formed on a semiconductor substrate 1, a polycrystalline silicon layer is formed thereon, and is patterned as prescribed, thereby forming a gate electrode 6. Further, with the electrode 6 as a mask an oxidized film 5 is selectively etched to allow a gate oxidized film 7 to remain directly under the mask. With the electrode 6 as a mask the reverse conductive type impurity to the substrate 1 is injected, thereby forming the source 8 and the drain 9 to obtain a semiconductor device 10.

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing an MOg type semiconductor device.

Generally, an MOa type semiconductor device consisting of a field effect transistor is provided with a protection diode within one chip.

Therefore, when forming this protection diode (:, MOg
The region where the conductor element is to be formed is contaminated with impurity C2, and therefore, in the MOa type semiconductor device for high frequency use,
In order to achieve low power transfer with little loss in a high frequency band (4), a semiconductor substrate with a substrate resistance of several tens of ohms is normally used, and its impurity concentration is set to be low. However, during the oxidation treatment and impurity treatment in the above-mentioned protective diode formation process and the source/drain formation process of the MO8 type semiconductor element, impurities of the opposite #electronic type to the semiconductor substrate may be used to form the gate of the semiconductor substrate. introduced into the region by external diffusion. (See Figure 1) The depth of introduction of this impurity usually reaches several microns, and after the formation of the gate oxide film, ion implantation, etc. This has the disadvantage that it is only possible to control the impurities 11 in the vicinity and that it is not possible to obtain an MO8 type semiconductor device having predetermined collector characteristics.

The present invention has been made in view of the above points, and has excellent device characteristics by keeping the region where the gate is to be formed identical to the semiconductor substrate and having a predetermined concentration of impurities introduced therein. MO that can easily form semiconductor confectionery
A method for manufacturing an A-type semiconductor device has been discovered.

Examples of the present invention will be described below.

FIG. 2 (At(2) As shown in FIG.
Oxidized Ml on the surface of! ! Next, a region of the oxidized Ps2 corresponding to the gate formation region 3 is opened using a well-known etching method. Gate formation area 3 (
2. An impurity of the same conductivity type as the semiconductor substrate 1 is introduced to form an impurity region 4 of a predetermined concentration.

Here, the impurity concentration introduced into the gate formation region 3 is as shown by curve (I) in % of FIG.

Source 8, which will be described later. After the step of forming the drain 9, the heat treatment removes C2 and externally diffuses the source 8, drain 9, etc. into the region 3 where the gate is to be formed. In the figure, the curve (I[)
The diffusion depth of this impurity region 4 is set to be deeper than the depth of introduction of the impurity in external diffusion (2) shown in curve 1 (U).

Next, as shown in IBI of the figure, a new oxide film 5 is formed on the surface of the heat-treated semiconductor substrate 1.

Next, as shown in FIG. 101, the source 8 of the oxide film 5,
Windows 8m and 9m are opened by photolithography in a portion corresponding to the region where the drain 9 is to be formed, and impurities of the opposite conductivity type to the semiconductor substrate 1 are introduced to form regions of a high concentration source 8m and a high concentration drain 9m. do.

Next, a new oxide film is formed on the semiconductor substrate 1, and a polycrystalline silicon layer for forming the gate electrode 6 is formed on this oxide film, and this polycrystalline silicon layer is subjected to predetermined patterning. This is referred to as gate electrode 6.

Next, the gate electrode 6 is masked and the oxide film 5 is selectively etched so that the gate oxide By remains directly below it. After that, as shown in the same figure (), game) m&
6 as a mask (conducting impurities of the opposite conductivity type to the two-handed conductor substrate 1 to form a source 8 and a drain 9, and forming a semiconductor device 10).
get.

In the semiconductor device 10 manufactured in this way, impurities of the same conductivity type as the gate formation region 3 (the second conductor substrate 1) are introduced in advance at a predetermined diffusion depth, so that the source 8
During the heat treatment after forming the drain 9, the semiconductor substrate 1 is introduced into the gate formation region 3 (2) by external diffusion from the drain 9b.
It is possible to maintain a predetermined impurity concentration C2 in the gate region by compensating for impurities of opposite magnetic type.

As a result, a so-called low output capacitance MOa type half-type semiconductor metal piece with little loss even when used in a high frequency band can be obtained, and a semiconductor device 10 having extremely excellent device characteristics can be realized.

In the embodiment, a case has been explained in which external diffusion of the source 8 and drain 9 is prevented. Of course, the method of the present invention can also be applied to the case where the protective diode formation process (= gate formation area 3 (2) and the above-mentioned impurity area 4 may be formed.

As explained above, 1. Invention C: According to the method for manufacturing an MOa type semiconductor device, the region where the gate is to be formed is maintained in a state where impurities of a predetermined concentration of the same conductivity type as the semiconductor substrate are introduced, resulting in an excellent device. It has remarkable effects such as being able to easily form a semiconductor element having specific characteristics.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between the impurity concentration in the gate region of a MOB type semiconductor device manufactured by a conventional method and the depth direction of the substrate. FIG. 3 is an explanatory diagram showing the relationship between the impurity concentration of the gate region of the MOa type semiconductor device manufactured by the method C2 of the present invention and the depth direction of the substrate. be. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2, 6... Oxide film, 3... Gate formation area, Ja... Opening, 4... Impurity -
Dynamic region, 6... Gate 'lIL pole, 7... Gate oxide film, 8... N-7,, Jb... High concentration source, 9
...Train, 9b...High degree drain, 10...
・MO8 type semiconductor device. Applicant's representative Patent attorney Takehiko Suzue 1st Fl! J Figure 3

Claims (1)

[Claims] A method for manufacturing an MOa type semiconductor device, comprising the step of introducing an impurity of the same conductivity type as that of the semiconductor substrate into a region of a semiconductor substrate of one conductivity type where a gate is to be formed, before an element formation step.