| 摘要 |
PROBLEM TO BE SOLVED: To prevent formation of a recessed section in the edge section of an embedded oxide film when a trench is formed on the surface of a silicon substrate. SOLUTION: The projections and steps on an buried oxide film 107''', which occur after a silicon nitride film 103'' is removed, is reduced by anisotropically etching a silicon oxide film 107' buried in a trench section by using a silicon nitride film 103 as a mask. Consequently, the edge section of the silicon oxide film 107' maintains a smooth surface and constrictions can be eliminated. Therefore, reliability of a gate oxide film is improved.
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