Patent ID: 7034366

Claim:
A semiconductor device, comprising: a semiconductor substrate; a gate electrode formed on said semiconductor substrate via a gate insulating film; a source region and a drain region of a first conductivity type formed on both sides of said gate electrode, respectively, in said semiconductor substrate; and a punch-through stopper region of a second conductivity type formed in said semiconductor substrate such that said second conductivity type punch-through stopper region is located between said source region and said drain region at distances from said source region and said drain region and extends in a direction perpendicular to a principal surface of said semiconductor substrate, wherein a concentration of an impurity element of the second conductivity type in said punch-through stopper region is set to be at least five times greater than a substrate impurity concentration between said source region and said drain region, said punch-through stopper region being formed such that a bottom of the punch-through stopper region is located in the vicinity of a well located underneath said source and drain regions and such that a bottom edge of said source and drain regions is located closer to a top of said punch-through stopper as compared with said bottom of said punch-through stopper.