Fabrication process for semiconductor device

Abstract

Provided is an improved fabrication process for a semiconductor device by means of which in fabrication of insulated gate semiconductor devices having gate insulating films including silicon oxide films of different thickness, no contamination from a photoresist is ensured in a silicon oxide film, generation of defects in the silicon oxide film to be otherwise caused by aqueous solution treatments is suppressed, and thereby variability of characteristics among the semiconductor devices is suppressed. A silicon oxide film of a gate insulating film is formed on a semiconductor surface, a silicon nitride film is formed thereon by means of a chemical vapor deposition method using monosilane and ammonia as a source gas prior to formation of a resist film, the resist film is selectively formed on the surface, part of the silicon nitride film not covered by the resist film and the silicon oxide film therebeneath are removed to expose a semiconductor surface, the exposed semiconductor surface is oxidized to form a second silicon oxide film having a thickness different from that of the previously described silicon oxide film, and gate electrodes are formed on the respective insulating films.