| 摘要 |
PROBLEM TO BE SOLVED: To obtain a semiconductor device manufacturing method with which the accelerated diffusion of impurities by thermal oxidization can be suppressed, the degradation in characteristic of a transistor can be prevented by preventing the thickening of a gate insulating film, the lowering of breakdown voltage and the lowering of yield of production of the gate insulating film can be prevented, and the controllability of threshold voltage of an MOSFET can be improved. SOLUTION: The first gate electrode film 4g is formed on the first gate oxide film 3a, and, after the first gate electrode film 4g has been patterned, the second gate oxide film 3b is formed by performing thermal oxidization utilizing the first gate electrode film 3b as a heat resisting oxide film. Besides, after the second gate electrode 4h has been formed on the whole surface, the first and the second gate electrode films 4g and 4h are flattened using a CMP method, and then they are patterned into the form of desired gate electrode.
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