SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a semiconductor device having high breakdown strength which can be employed in a high side driver semiconductor device for driving a high side switch. SOLUTION: A lateral MOSFET is formed in an n<-> type semiconductor epitaxial layer 2 grown on a p type semiconductor substrate 1. On the major surface side in the n<-> type semiconductor epitaxial layer 2, a field relaxing region 10 comprising a lightly doped p<-> region is formed between a p-type region 5 for forming channel and an n<+> type drain region 6. A CMOS is formed on the major surface side of a p<+> isolation region 7 and an element forming region comprising the n<-> type semiconductor epitaxial layer 2 isolated by the p type semiconductor substrate 1. Impurity density of the n<-> type semiconductor epitaxial layer 2 is set in the range of 2.5×10<12> -4.0×10<12> cm<-2> and the impurity density of the field relaxing region 10 is set in the range of 1.0×10<12> -3.0×10<12> cm<-2> .