A p−-type isolation region is provided at a part between a p-type ground region and a circuit region (a high potential region and an intermediate potential region) in an n-type well region. The p−-type isolation region is electrically connected with a H-VDD pad and an n+-type drain region of a HVNMOS. The p−-type isolation region has between n+-type pickup connect regions and between n+-type drain regions of two of the HVNMOSs, a protruding part (a T-shaped part, an L-shaped part, a partial U-shaped part) or an additional part that protrudes toward a p-ground region.