JPS6197866A - Mos type semiconductor memory device - Google Patents

Abstract

PURPOSE:To contrive the increase in writing times and the prolongation in memory hold time by forming an Si oxide film, an Si nitride film or an Si oxide film containing Si nitride, and an Si oxide film around a floating gate. CONSTITUTION:Source and drain diffused layers 3 and 4 of field oxide films are formed in the surface of an Si substrate 1. Further, an Si oxide film 6, an Si nitride film 7, and an Si oxide film 8 are formed around the floating gate electrode 5; thus, the insulation film is partly changed into the gate film on the Si substrate 1. This manner can reduce the intra-insulation-film level and the interfacial level and then enables the prolongation in memory hold time and the increase in writing times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a floating gate protective film structure for a 70-gate MOS type semiconductor memory device.

[Conventional technology]

Conventionally, a peripheral protective film in a 70-Ting Gate (MO-8) type semiconductor memory device has generally been formed of a silicon oxide film.

However, according to the above-mentioned conventional technology, the electrons accumulated in the floating gate leak through the levels in the silicon oxide film, and in particular, electron leakage is more severe to the surface or top surface of the floating gate than to the semiconductor substrate side.
As a result, there have been disadvantages such as a shortened memory protection time and a reduced number of write operations in the floating GMOS type semiconductor memory device.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and to provide a 70-gate MOS semiconductor memory device which can be written many times and has a long memory retention time.

〔overview〕

The basic structure of the present invention for achieving the above object is that in a floating gate MO3 type semiconductor memory device,
There is a silicon oxide film around the floating gate,
It is characterized in that a silicon nitride film or a silicon oxide film containing silicon nitride is formed, and a silicon oxide film is further formed.

[Metal practice]

Hereinafter, the present invention will be explained in detail using actual wAH.

FIG. 1 is a sectional view of a main part of a floating gate MOS type conductor memory device showing one embodiment of the present invention. That is, source and drain diffusion layers 5.4 of a field oxide film are formed on the surface of the 81 substrate 1, and silicon oxide film is further formed around the floating gate electrode 5.
! A silicon nitride bib 7 is formed by treating 6t silicon oxide in an ammonia atmosphere at 1000°C, and a silicon oxide film 8 is further formed, and a part of the marginal conjunctiva is formed by 8.
It is formed as a gate film on one substrate 1.

Note that the silicon nitride film 7 may be a cell silicon oxide film containing silicon nitride.

Furthermore, the present invention has a structure in which the gate film on the drain side is partially thinned
Needless to say, it can also be applied to XIIiPROM.

〔effect〕

As in the present invention, by protecting the periphery of the floating gate with a three-layer structure film of silicon oxide film, silicon nitride film, and silicon oxide film, it is possible to reduce the level in the fine film and the level at the interface. 74-ting game) MO5IJ
This has the effect of extending the memory retention time of the semiconductor memory device and increasing the number of writes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a fluting/MOS semiconductor memory device showing one embodiment of the present invention. 1...81 Substrate 2...Field oxide film 5.4...Diffusion layer 5...Funging gate electrode 6.8...
...Silicon oxide film 7...Silicon nitride film

Claims (1)

[Claims] A MOS type semiconductor memory device characterized in that a silicon oxide film, a silicon nitride film or a silicon oxide film containing silicon nitride are formed around a floating gate, and a silicon oxide film is further formed.