| 摘要 |
PROBLEM TO BE SOLVED: To form a thin gate oxide film and a thick gate oxide film in one step for forming the gate oxide film. SOLUTION: A sacrifice oxide film 32 is formed at the surface of each element forming region 14a, 14b on a substrate 10. Subsequently, by implanting nitrogen into the element forming region 14a for forming elements having the thin gate oxide film via the sacrifice oxide film 32, a shallow nitrogen implantation part 38 is formed at the upper part of a well 16a of this element forming region 14a (fig. 2 (1)). Next, after the sacrifice oxide film 32 is etched and removed, a substrate 10 is heated in an oxidizing atmosphere, and the surfaces of wells 16a, 16b are oxidized. As a result, the thin gate oxide film 40 is formed in the element forming region 14a having the nitrogen implantation part 38. The thick gate oxide film 42 is formed in the element forming region 14b where nitrogen has not been implanted.
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