Patent ID: 7436024

Claim:
A semiconductor device comprising: a semiconductor layer of a first conductivity type; a first semiconductor region of a second conductivity type in the surface portion of the semiconductor layer; a drain region of the second conductivity type in the first semiconductor region; a second semiconductor region of the second conductivity type in contact with or overlapping with the first semiconductor region; a channel region of the first conductivity type in the surface portion of the second semiconductor region; a source region of the second conductivity type in the channel region; and a gate electrode above the channel region between the source region and the first semiconductor region with a gate insulator film interposed therebetween, wherein the net total impurity amount in the first semiconductor region is smaller than the net total impurity amount in the second semiconductor region, and wherein, under the gate electrode between the drain region and the channel region, an impurity concentration in a channel region side of the second semiconductor region is higher than the impurity concentration of the first semiconductor region.