JPH0247838A - Manufacture of mos type semiconductor device - Google Patents

Abstract

PURPOSE:To realize high speed advancement of operation and high integration and to improve breakdown strength between a gate electrode and a drain electrode by forming a thick oxide film with a gate insulating film, being formed shorter than the gate length, as a mask, and forming a gate electrode such that its both ends overlap this. CONSTITUTION:A silicon oxide film 3 and a silicon nitride film 4 on a silicon substrate 1 are etched, and a gate insulating film which is shorter than the gate electrode length is formed at a gate electrode formation position. The nitride film 4 is used as a mask 4 so as to selectively oxidize the surface of the silicon substrate, and the thickness of an oxide film 2a is made thicker than that of the gate insulating film. By a selective etching method, a gate electrode 5 is formed such that it protrudes beyond the films 4 and 3 to their both sides on the gate insulating film and the silicon oxide film 2a and its both end parts overlap the silicon oxide film 2a. For this reason, it can cope with high speed advancement of operation and high integration of a MOS type semiconductor device, and also breakdown strength between the gate electrode 5 and the drain electrode is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a MOS semiconductor device (insulated gate field effect transistor), and particularly to a method for forming a gate insulating film.

[Conventional technology]

In recent years, MOS semiconductor devices have been miniaturized to achieve faster operation and higher integration. However, when the gate length of a MOS transistor is shortened, the substrate concentration must be reduced to prevent punch-through. It is necessary to increase the height and make the gate insulating film thinner.

FIGS. 2A to 2C are vertical cross-sectional views showing manufacturing steps before and after forming a gate electrode in a conventional MOS semiconductor device.

First, as shown in FIG. 2(a), a field oxide film 12 is formed on a silicon substrate 11 to define an element region. Then, a silicon oxide film 13 and a silicon nitride film 14, which will serve as a gate insulating film, are formed on the entire surface.

Next, as shown in FIG. 2(b), polycrystalline silicon 1 is applied to the entire surface.
5 is grown, and a photoresist 17 is patterned in the gate electrode formation region thereon.

Then, as shown in FIG. 2C, polycrystalline silicon 15 is selectively etched using photoresist 17 as a mask to form gate electrode 15. Furthermore, this gate electrode 15
The silicon substrate 11 is
Impurities are ion-implanted to form the drain and source regions 16 of the transistor.

[Problem to be solved by the invention]

The MOS type semiconductor device formed by the above-mentioned manufacturing method is
Silicon oxide film 1 with a uniform thickness under the gate electrode 15
3 and a silicon nitride film 14 is formed. For this reason, when the gate insulating film is made thinner in order to speed up the operation and increase the integration of MOS semiconductor devices, the gate insulating film on the drain side also becomes thinner, and the withstand voltage between the gate electrode and the drain electrode decreases. There's a problem.

It is an object of the present invention to provide a method for manufacturing a MOS type semiconductor device that improves the breakdown voltage between the gate electrode and the drain electrode while increasing the operation speed and integration.

[Means for Solving the Problems] A method for manufacturing an MO5 type semiconductor device of the present invention includes forming a gate insulating film having at least an insulating film that is difficult to oxidize on the surface on a semiconductor substrate, and using this gate insulating film as a gate electrode. forming an oxide film on the surface of the semiconductor substrate using the gate insulating film as a mask, forming an oxide film thicker than the gate insulating film on the surface of the semiconductor substrate; The method includes a step of forming a gate electrode on the gate insulating film in an overlapping manner, and a step of forming a drain/source region using the gate electrode.

[Function] According to the manufacturing method described above, a MOS transistor is manufactured which has a thin gate insulating film directly under the gate electrode and a thick gate insulating film below both ends of the gate electrode.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a) to 1(d) are longitudinal cross-sectional views showing an embodiment of the present invention in the order of steps, and particularly show the manufacturing steps before and after the formation of Day 1 electrodes.

First, as shown in FIG. 1(a), a field oxide film 2 is formed on a silicon substrate 2 to define an element region. Next, a silicon oxide film 3 and a silicon nitride film 4 are grown on the entire surface to form a thin insulating film.

Then, a photoresist 7 is selectively formed at the gate electrode formation position of the MOS transistor to a length shorter than the gate electrode to be formed.

Next, as shown in FIG. 1(b), the silicon oxide film 3 and silicon nitride film 4 are etched using the photoresist 7 as a mask to form a gate insulating film shorter than the gate electrode length at the gate electrode formation position. do.

Next, as shown in FIG. 1(C), the silicon nitride film 4 is
is used as a mask to selectively oxidize the silicon substrate surface.

At this time, the thickness t of the selectively oxidized silicon oxide film 2a
l is formed to be thicker than the thickness t2 of the gate insulating film made of the silicon oxide film 3 and silicon nitride film 4.

Then, as shown in FIG. 1(d), a gate electrode 5 is formed on the gate insulating film and silicon oxide film 2a by forming polycrystalline silicon over the entire surface and selectively etching using a photoresist.

At this time, since the silicon nitride film 4 and the silicon oxide film 3 are formed to be shorter than the gate electrode length, the gate electrode 5 protrudes beyond these films 4.3 to both sides.
Both ends thereof are formed so as to overlap silicon oxide film 2a.

Thereafter, the source/drain regions 6 of the transistor are formed by ion-implanting impurities using the self-line technique using the gate electrode 5.

Therefore, in the MOS type semiconductor device manufactured by this method, the gate insulating film directly under the gate electrode 5 is thin with a thickness t2, but on the source and drain sides, it is thickened to a thickness of 1+ by the silicon oxide film 2a. It has become. For this reason, most of the gate HJi region is composed of a thin gate insulating film, and while it can cope with higher operation speed and higher integration of MOS type semiconductor devices, especially the gate electrode 5. The gate insulating film between the gate electrode 5 and the drain region 6 is made thicker, and the breakdown voltage between the gate electrode 5 and the drain electrode (not shown) is improved.

Note that the breakdown voltage between the gate electrode and the drain electrode can be arbitrarily controlled by adjusting the thickness t of the silicon oxide film 2a.

Note that in this embodiment, the gate insulating film is a silicon oxide film 3.
Although a two-layer structure consisting of the silicon nitride film 4 and the silicon nitride film 4 is used, it is also possible to form the gate insulating film only with the silicon nitride film, and the number of steps can be reduced.

[Effects of the Invention] As explained above, the present invention forms a thin gate insulating film with a length shorter than the gate length, and then forms a thick oxide film using this gate insulating film as a mask. Since the gate electrode is formed so that both ends overlap the film, an MO with a thin gate insulating film directly below the gate electrode and a thick gate insulating film below both ends of the gate electrode is formed.
An S-type transistor can be formed, and a MOS-type semiconductor device with improved breakdown voltage between a gate electrode and a drain electrode can be manufactured while achieving higher operation speed and higher integration.

[Brief explanation of the drawing]

1(a) to 1(d) are vertical cross-sectional views showing the manufacturing steps before and after forming the gate electrode of the MO8 type semiconductor device of the present invention, and FIG. 2(a) to 2(c) are the conventional FIG. 3 is a vertical cross-sectional view showing manufacturing steps before and after forming a gate electrode of a MOS type semiconductor device. 1.11...Silicon substrate, 2,12...Field oxide film, 2a...Silicon oxide film, 3.13...
Silicon oxide film, 4.14... silicon nitride film, 5.
15... Gate electrode (polycrystalline silicon), 6.16.
...Source/drain region.

Claims (1)

[Claims] 1. Forming a gate insulating film having at least an insulating film that is difficult to oxidize on the surface on a semiconductor substrate, and patterning this gate insulating film to a length shorter than the gate electrode length, and masking this gate insulating film. forming an oxide film thicker than the gate insulating film on the surface of the semiconductor substrate; forming a gate electrode on the gate insulating film so that both ends overlap the thick oxide film; 1. A method for manufacturing a MOS semiconductor device, comprising the step of forming drain and source regions using electrodes.