Patent ID: 7687855

Claim:
A semiconductor device comprising: a semiconductor substrate having a first conductivity type; a source region and a drain region having a second conductivity type formed in the semiconductor substrate; a channel region of the first conductivity type formed between the source region and the drain region; an impurity region of the first conductivity type formed below the channel region and overlapped only with the source region in the semiconductor substrate, the impurity region extending at least half way across a width of the channel region near to the drain region without being in contact with the drain region in a direction of <100> axis in the {100} plane of the semiconductor substrate; a gate insulating film formed over the semiconductor substrate; and a gate electrode formed over the gate insulating film, wherein the impurity region is not in contact with the gate insulating film, and wherein the drain region is in contact with a region of the first conductivity type having a first concentration of impurities same as the channel region.