| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device in which electric field concentration hardly occurs in a thermally oxidized Si film in edge sections. SOLUTION: A first thermally oxidized Si film 11 is formed in a tapered shape 12 and the edge section of a first polycrystalline silicon film 3 is worked to a tapered shape 14 by using the tapered film 11 as a mask. In a thermally oxidizing process thereafter, the edge section of the polycrystalline silicon film 3 is rounded and a second thermally oxidized Si film 4 is formed on the rounded first polycrystalline silicon film 3. Since the edge section of the film 3 is rounded, edge section of the second thermally oxidized Si film 4 can be prevented from becoming thinner in thickness and, accordingly, the occurrence of electric field concentration in the film 4 can be prevented.
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