| 摘要 |
PROBLEM TO BE SOLVED: To make the breakdown strength of a gate oxide film higher at the bottom than at the side wall used a channel. SOLUTION: An n+ substrate where the board face azimuth constitutes (110) is prepared, and it is arranged such that a sidewall where a channel is to be formed out of a trench 6 is a face (100), and that other sidewall is a face (110). By doing it this way, the growth speed of a gate oxide film 7 becomes higher at other sidewall and the bottom than at the sidewall to serve as the section where the channel is made out of the trench 6, and it is made thicker there. Therefore, the high mobility of the channel can be secured, and also the breakdown drop due to the partial thinning of the gate oxide film 7 can be prevented, too, Hereby, it becomes possible to make compatible the lowering of ON resistance of a power MOSFET and the high breakdown strength.
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