Power semiconductor device having RESURF layer

A semiconductor device comprising:

• a drain layer having a first conductivity type;
• a first drift layer having the first conductivity type and formed on the drain layer;
• second drift layers having the first conductivity type and RESURF layers having a second conductivity type, which are formed on the first drift layer and periodically arranged in a direction perpendicular to a direction of depth, the RESURF layer forming a depletion layer in the second drift layer by a p-n junction including the second drift layer and RESURF layer, and the first drift layer having an impurity concentration different from that in the second drift layer;
• a drain electrode electrically connected to the drain layer;
• a base layer having the second conductivity type and selectively formed in surface regions of the second drift layer and RESURF layer;
• a source layer having the first conductivity type and selectively formed in a surface region of the base layer;
• a source electrode formed in contact with surfaces of the base layer and source layer;
• and
• a gate electrode formed on the base layer located between the source layer and the second drift layer with a gate insulating film interposed therebetween.