FIELD-EFFECT SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To reduce on resistance without deteriorating of avalanche breakdown in a power MOS (metal, oxide film, and semiconductor) FET. SOLUTION: An N+ semiconductor region 12 is formed at a lower part 3a of a p-type diffusion region 3 where a channel is generated. The N+ semiconductor region 12 is formed in a region from one main surface of a semiconductor layer 100 to the lower part 3a of the p-type diffusion region 3. The concentration of impurities of the N+ semiconductor region 12 should be set higher than that of an N- semiconductor region 2.