Patent ID: 7157772

Claim:
A semiconductor device comprising: an SOI layer formed on a supporting substrate with a buried oxide film placed therebetween; a body region of a first conductive type selectively formed in a main surface of the SOI layer; a source region of a second conductive type formed in a main surface of the body region; a drain region of the second conductive type formed in the main surface of the SOI layer so as to be adjacent to the body region; an element isolating film formed on the drain region; a gate oxide film formed on a region of the main surface of the SOI layer between the source region and the element isolating film; a drain electrode connected to the drain region; a gate electrode which is formed on the gate oxide film and a part of the element isolating film and is extended in a drain region direction so as to have a first end over the part of the element isolating film; an insulating film covering the gate electrode and the element isolating film; and a source electrode which is formed on the insulating film so as to be connected to the source region and is extended in the drain region direction further than the first end of the gate electrode so as to have an end portion above the drain region, wherein a first thickness of the insulating film at a position over the first end of the gate electrode is smaller than a second thickness of the insulating film at a position below the end portion of the source electrode above the drain region the first thickness is smaller than a third thickness of the insulating film at a position on a second end of the gate electrode above the body region, and the first thickness is equal to a fourth thickness of the insulating film at a position over the part of the element isolating film between the first end of the gate electrode and the end portion of the source electrode above the drain region.