| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device wherein a breakdown strength is improved with no on-resistance increased. SOLUTION: A p-type well region 4 and an n+ type drain region 2, away from each other, are formed in an n-type semiconductor layer 1 on an insulating layer 11, and an n+ type source region 3 is formed in the p-type well region 4. The p-type well region 4 is formed as deep as the insulating layer 11 from the surface of the n-type semiconductor layer 1. A source electrode 8 is so formed as to bridge between the n+ type source region 3 and a p+ type base contact region 9 in the p-type well region 4. Since a rough is provided at an interface S1 between the insulating layer 11 and a semiconductor layer on it, in other words, at the interface between the insulating layer 11 and the n-type semiconductor layer 1 as well as at the interface between the insulating layer 11 and the p-type well region 4, the area of interface S1 is larger compared to a case of flatness.
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