| 摘要 |
A power MOSFET comprising a drain layer (12) having a first conductivity type, a drift layer (8) having the first conductivity type provided on the drain layer, a base layer (10) having a first or a second conductivity type provided on the drift layer, source regions (16a, 16b) having the first conductivity type provided on the base layer, gate insulating films (2a, 2b) formed on the inner wall surface of trenches (Ta, Tb), the gate insulating films (2a, 2b) penetrating the base layer and reaching the drift layer, gate electrodes (4a, 4b) provided inside the trench through the gate insulating film, wherein the gate insulating film is formed such that the portion adjacent to the drift layer is thicker than the portion adjacent to the base layer, and the drift layer (8) has a concentration gradient higher in the vicinity of the drain layer (12) and lower in the vicinity of the base layer (10) along a depth direction of the trench (Ta, Tb). <IMAGE>
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