| 摘要 |
PROBLEM TO BE SOLVED: To enable a laminated film, composed of an oxide film and a nitride film to be formed as a gate insulating film on the inner wall of a trench to obtain a semiconductor device of high breakdown voltage and to relax the concentration of an electric field on the upper part and bottom of the trench, so as to prevent the upper part and bottom of the trench from deteriorating in breakdown voltage. SOLUTION: A transistor has a trench gate structure, where a gate insulating film formed on the inner wall of a trench 6 is formed of a laminated film, composed of an oxide film 7a, a nitride film 7b, and an oxide film 7c at the sidewall of the trench 6 and thick oxide films 7d and 7e at the upper part and bottom of the trench 6.
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