Claims
- 1. A method of forming a vertical-type double diffused field effect transistor comprising the steps of:
- covering a silicon layer of one conductivity type with a first silicon oxide film, said silicon layer having an element formation area and a peripheral area, wherein said first silicon oxide film has a first portion formed on said element formation area and a second portion formed on said peripheral area of said silicon layer;
- forming a silicon nitride film on said first portion of said first silicon oxide film substantially excluding said second portion of said first silicon oxide layer;
- introducing impurities into said peripheral area of said silicon layer except said element formation area of said silicon layer to thereby form a first region of a conductivity type opposite to said one conductivity type in said peripheral area;
- thickening said second portion of a first silicon oxide film to form a second silicon oxide film by using said silicon nitride film as a mask, said second silicon oxide film being thereby formed on said first region;
- removing said silicon nitride film and said first portion of said first silicon oxide film to expose a surface of said element formation area of said silicon layer with said second silicon oxide film remaining on said first region;
- forming a gate oxide film on said surface of said element formation area of said silicon layer in contact with said second silicon oxide layer;
- forming a conductive layer which has a portion formed on a part of said gate oxide film and is elongated over said second silicon oxide film; and
- forming a second region of said opposite conductivity type in said element formation area of said silicon layer at a distance from said first region.
- 2. The method as claimed in claim 1, wherein said silicon nitride film is formed by forming an original silicon nitride film on said first and second portions of said first silicon oxide film and then removing a portion of said original silicon nitride film from said second portion of said first silicon oxide film by using a photo-resist film formed on a remaining portion of said original silicon nitride film as a mask, and said impurities being implanted into said peripheral area of said silicon layer by using said photo-resist film as a mask.
Priority Claims (1)
Number |
Date |
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3-209700 |
Aug 1991 |
JPX |
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Parent Case Info
This application is a continuation of Application Ser. No. 07/933,249, filed Aug. 21, 1992 now abandoned.
US Referenced Citations (9)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0046552 |
Feb 1987 |
JPX |
Continuations (1)
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Number |
Date |
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Parent |
933249 |
Aug 1992 |
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