In order to improve the characteristics of the high breakdown voltage MOS, a
semiconductor
device of the present invention is characterized in that an LDMOS transistor, which
comprises a source region 4, a channel region 8, and a drain region
5, and a gate electrode 7 formed on the channel region 8,
and a drift region formed between the channel region 8 and the drain region
5, wherein an N--type low concentration layer 22 serving
as the drift region is formed shallowly at least below the gate electrode 7
(first N--type layer 22A) but formed deeply in a neighborhood
of the drain region 5 (second N--type layer 22B).
