Patent ID: 8159036

Claim:
A semiconductor device, comprising: a LDMOS transistor, the LDMOS transistor comprising: a semiconductor layer of a first conduction type; a gate electrode formed on said semiconductor layer via an insulator layer; a sidewall insulator film formed on sides of said gate electrode; an LDD layer of a second conduction type located in the surface of said semiconductor layer beneath said sidewall insulator film; a source layer of the second conduction type formed in the surface of said semiconductor layer at a position adjacent to said LDD layer; a resurf layer of the second conduction type formed in the surface of said semiconductor layer at a position sandwiching said gate electrode with said LDD layer, said resurf layer formed under said sidewall insulator film; and a drain layer of the second conduction type formed in the surface of said semiconductor layer at a position adjacent to said resurf layer, wherein said resurf layer includes a first resurf layer having a peak of a first impurity concentration and a second resurf layer formed below the first resurf layer and having a peak of a second impurity concentration, wherein said peak of said first impurity concentration is smaller than said peak of said second impurity concentration, and the cross-section of the second resurf layer in a plane perpendicular to the surface of said semiconductor layer is larger than that of the first resurf layer in a plane perpendicular to the surface of said semiconductor layer.