| 摘要 |
An N<-> type epitaxial layer is formed on a P<-> type silicon substrate. Trenches are created so as to penetrate N<-> type epitaxial layer and so as to reach to a predetermined depth of P<-> type silicon substrate. Thermal oxide films are formed on the sidewalls of trenches. Buried polysilicon films are formed so as to fill in trenches. Thermal oxide films are formed having an approximately constant film thickness ranging from the bottoms to the edges of the openings of trenches so as not to give stress to N<-> type epitaxial layers. Thereby, a semiconductor device wherein a leak current is prevented can be gained.
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