FORMATION OF SILICON OXYNITRIDE FILM OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a method for forming a silicon oxynitride film which may be used as a gate insulating film. SOLUTION: First, an initial oxide film 103 is formed on a semiconductor substrate 101, and thereafter the initial oxide film 103 is converted into a pure oxide film and is grown concurrently. The pure oxide film is converted into a silicon oxynitride film and at the same time, the silicon oxynitride film is grown under a temperature of 700 to 950 deg.C and is then formed in a thickness of 40 to 200 on the semiconductor substrate 101. The silicon oxynitride film is formed by injecting oxidized nitrogen gas to a diffusion furnace, for example, to a vertical type diffusion furnace.