| 摘要 |
PROBLEM TO BE SOLVED: To prevent the reliability of a gate oxide film being degraded by a method wherein the film thickness of an initial oxide film, which is formed by the time of a loading-in-furnace and heat-up process, is controlled so that the film thickness's rate occupying to the film thickness of the gate oxide film is limited in a specified range. SOLUTION: The material for a gate oxide film is put in a furnace in 1% of oxygen/ inert gas (nitrogen gas, argon gas or the like) atmosphere at a temperature of 300 to 700 deg.C, for example, in the oxidation sequence of the five stages of loading-in-furnace→heat-up→oxidation→cooling-down→unloading-from-furnace and after the material is heated up until a temperature of 750 to 900 deg.C in 100% of inert gas (nitrogen gas, argon gas or the like) atmosphere, an oxidation (a wet oxidation, a dry oxidation, a hydrochlorolic acid oxidation, a DEC oxidation, an NO oxidation, an N2O oxidation or the like) is performed on the material at a temperature of 750 to 900 deg.C to form a gate oxide film. At this tine, the film thickness of an initial oxide film, which is formed by the time of a loading-in-furnace and heat-up process, is controlled in a thickness to 20-40% of the film thickness of the gate oxide film. In such a way, by suppressing the film thickness of the initial oxide film of bad quality in a thickness thinner than 40% of the film thickness of the gate oxide film, the reliability of the gate oxide film is remarkedly enhanced.
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