| 摘要 |
PROBLEM TO BE SOLVED: To form a high Vth MOSFET and a low Vth MOSFET having gate insulating films with different thicknesses without coating the gate insulating films with a resist. SOLUTION: A silicon oxide film 3 is etched and removed from a low Vth region (b). Nitriding is performed to form a nitride film 4 on the low Vth region (c). Without forming a resist film, a silicon oxide film 3 is etched and removed from a high Vth region (d). A semiconductor substrate 1 is subjected to thermal oxidation to form a thick gate insulating film (5) on the high Vth region and a thin gate insulating film (6) on the low Vth region (e). A gate electrode is formed and an impurity diffusion layer 8 used as source/drain regions is formed (f).
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