Patent ID: 7339234

Claim:
A semiconductor device comprising an LDMOS transistor, said LDMOS transistor comprising: a gate insulation film formed over a semiconductor substrate; a gate electrode formed over said gate insulation film; a drain well of a first conductivity type formed in said semiconductor substrate so as to include a gate region covered with said gate electrode; a channel well of a second conductivity type opposite to said first conductivity type formed in said drain well in a partially overlapped relationship with said gate region; a source region of said first conductivity type formed in said channel well in an overlapping manner or adjacent with a side surface of said gate electrode; a medium-concentration drain region of said first conductivity type having an intermediate concentration level and formed in said drain well at a side opposing to said source region in a manner partially overlapping with said gate region, said medium-concentration drain region being formed with separation from said channel well; a drain region of said first conductivity type formed in said medium-concentration drain region with a separation from said gate region; a low concentration well of said second conductivity type formed inside said drain well so as to include at least a part between said channel well and said medium-concentration drain region.