| 摘要 |
An N drift region (42) is provided in its surface with a P+ well region (43) of a square ring shape and a P region (51) formed in the center of the square ring. The P region (51) is relatively low in impurity concentration and relatively small in thickness while the P+ well region (43) is relatively high in impurity concentration and relatively large in thickness. The P region (51) of low impurity concentration is lower in built-in voltage than P+ well region (43) of high impurity concentration, so that most part of a forward current of a diode consisting of the N drift region (42) and the P+ well and P regions (43, 51) can flow through the P region (51). Because of the low impurity concentration and small thickness of the P region (51), the rate of minority carriers in the forward current is low. Thus, a reverse recovery time of the diode can be shortened.
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