JPH0319285A - Mos type semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a MOS device having high drain current driving capacity by providing a polysilicon film on a gate thereby to form a channel in the film. CONSTITUTION:When a voltage of Vth or more is applied to a gate 3, a P-type Si substrate 1 under the gate 3 is inverted to an N type, and an N channel 7a is formed. Simultaneously, a P-type polysilicon film 5 on the gate is inverted to an N-type, and an N channel 7b is formed. When a positive voltage is applied to a lower drain region 4a and an upper drain region 6a in this state, drain currents flow from a lower source 4b through the channel 7a to the lower drain 4a and from an upper source 6b through the channel 7b to an upper source 6b. Channels 7a, 7b are not formed by the application of the voltage to the gate 3, and no drain current flows. A large quantity of drain current can flow with this arrangement.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a MOS type semiconductor device.

2. Description of the Related Art In recent years, MOS type semiconductor devices have been actively developed to meet the demand for lower power consumption as semiconductor devices become more highly integrated.

A conventional MOS type semiconductor device will be explained below with reference to FIG.

In FIG. 2, 11 is a p-type silicon substrate, 12 is an oxide film, 13 is a gate made of a polysilicon film, 14a is a drain region made of an n-type impurity diffusion layer, 14b is a source region made of an n-type impurity diffusion layer, and 17 is an n-channel formed by inverting a p-type silicon substrate.

Regarding the MOS type semiconductor device with the above precautions,
The operation will be explained below.

When a voltage exceeding the threshold value is applied to the gate electrode 13, the lower part of the gate 13 of the p-type silicon substrate 11 becomes n
The mold is inverted, forming an n-channel 17 through which conduction electrons can freely pass. Therefore, when a positive voltage is applied to the drain region 14a with this n-channel 17 formed, conduction electrons pass through the n-channel to the source region 14a.
A drain current flows from b to drain region 14a. However, when the voltage applied to the gate 13 is zero, the n-channel 17 is not formed, so no drain current flows. By changing the voltage applied to the gate 13 in this way, the drain current can be controlled.

Problems to be Solved by the Invention However, in the above-mentioned conventional structure, the part where the n-channel is formed is only the p-type silicon substrate part under the gate. The MOS type semiconductor device has a problem in that a large amount of drain current cannot flow through it.

The present invention solves the above-mentioned conventional problems, and aims to provide a MOS type semiconductor device that can obtain a large amount of drain current without increasing its area.

Means for Solving the Problems In order to achieve this object, the MOS type semiconductor of the present invention is as follows:
In addition to the channel in the semiconductor substrate, a polysilicon film insulated from the gate is formed on top of the gate.
It has a structure in which a channel can also be formed in the polysilicon film above the gate.

According to the configuration of the present invention, an n-channel obtained by applying a voltage higher than a threshold value to the gate is formed in both layers of the silicon substrate under the gate and the polysilicon film on the gate. Therefore, the amount of drain current can be increased, and the current drive capability of the MOS type semiconductor device can be improved.

EXAMPLE A MOS type semiconductor device according to the present invention will be described below with reference to FIG.

In Figure 1, 1 is a p-type silicon substrate, 2 is an oxide film,
3 is a gate made of a polysilicon film, 4a is a gate 1c in a silicon substrate. A lower drain region formed by an n-type impurity diffusion layer, 4b an upper drain region formed by a silicon substrate-internal dopant diffusion layer, 6b an upper source region formed by an n-type impurity diffusion layer in a polysilicon film, and 7a a p-type silicon substrate reversed. 7b is an n-channel formed by inverting the p-type polysilicon film.

The operation of the MOi9 type semiconductor device of this embodiment configured as described above will be described below.

First, when a voltage exceeding a threshold value is applied to the gate 3, the portion of the p-type silicon substrate 1 below the gate 3 is inverted to the n-type, forming an n-channel 7a through which conduction electrons can freely pass. At the same time as the case, the p-type polysilicon film 5 on the gate is also
The mold is inverted to form an n-channel 7b. Therefore,
With these n channels 7ai and 7b formed,
Lower drain region 4a'J? and top-drain region 6
When a positive voltage is applied to a, conduction electrons are transferred to n-channel 7a
from the lower source region 4b to the lower drain region 4a through the
to the upper saw region 6 through the n-channel 7b.
A side drain current flows from the lower drain region 6a to the lower drain region 6a through each path. However, when the voltage applied to the groove 3 is zero, the n-channels 7a and 7b are not formed, so the drain current does not flow much.

As described above, according to this embodiment, in addition to the n-channel in the semiconductor substrate under the gate, the polysilicon film is formed above the gate so that a large amount of drain current can flow. be able to.

In addition, in this example, since it is an n-channel type, a silicon substrate, a tp type polysilicon film on the gate, and
The diffusion layer for the source and drain regions is
However, in order to form a p-channel, the silicon substrate and the polysilicon film on the gate may be of n-type, and the diffusion layers for forming the source and drain regions may be of p-type.

Effects of the Invention According to the MOS type semiconductor device of the present invention, by providing a polysilicon film on the gate, a channel can be formed in the polysilicon film in addition to the channel in the silicon substrate under the b1 gate. M with high current drive ability
An OS type semiconductor device can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a MOS type semiconductor device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional MOSfi semiconductor device. DESCRIPTION OF SYMBOLS 1...P-type silicon substrate, 2...Oxide film, 3...Gate, 4a...Lower drain region, 4b...Lower Source area, 5...
... p-type polysilicon film, 6a ... upper drain region, 6b ... upper source region, 7a ...
...n channel, 7b...n channel, 11...p type silicon substrate, 12...
・Oxide film, 13...Gate, 14a...
・Drain region, 14b... Source region, 17
・・・・・・N channel.

Claims (2)

[Claims] (1) An insulating film is formed on a first polysilicon film that becomes a gate on a semiconductor substrate, and a second polysilicon film having a source region and a drain region is formed on this insulating film. A first polysilicon film is sandwiched between the semiconductor substrate and the second polysilicon film,
A MOS type semiconductor device characterized in that a channel is provided in a two-layer portion of the semiconductor substrate and the second polysilicon film. (2) The MOS type semiconductor device according to claim 1, wherein the insulating film is a surface oxide film of the first polysilicon film serving as the gate.