Semiconductor device with high withstand voltage and a drain layer having a highly conductive region connectable to a diffused source layer by an inverted layer

摘要

A highly conductive region 18 serving as a surface of a drain layer 2 of a first conductivity type is diffused more deeply than a main diffused layer 36 and a diffused channel layer 37, and has a small conducting resistance. The highly conductive region 18 is surrounded by a diffused region 40 of a second conductivity type which comprises a diffused base layer 38 and a diffused guard ring layer 13. Therefore, the highly conductive region 18 does not form spherical junctions, and a depletion layer spreading in the highly conductive region 18 extends into the highly conductive region 18. The highly conductive region 18 thus has a high withstand voltage while maintaining the low conducting resistance.