Patent ID: 6787848
Filing Date: 2004-09-07
Classification: H01L

Abstract:
A power MOSFET comprising:a drain layer of a first conductivity type; a drift layer of the first conductivity type provided on said drain layer; a base layer of a second conductivity type provided on said drift layer; a source region of the first conductivity type provided on said base layer; a gate insulating film formed on an inner wall surface of a trench penetrating the base layer and said drift layer and having a bottom portion reaching into the drain layer; and a gate electrode provided on said gate insulating film inside said trench, wherein said gate insulating film is formed such that a portion thereof adjacent to said drift layer is thicker than a portion thereof adjacent to said base layer, and said drift layer has an impurity concentration gradient higher in the vicinity of said drain layer and lower in the vicinity of said source region along a depth direction of the trench.