Patent ID: 7067878

Claim:
A field effect transistor, comprising: a semiconductor substrate of a first conductivity type; a gate insulation film formed on said semiconductor substrate; a gate electrode formed on said gate insulation film; a source electrode and a drain electrode formed at lateral sides, respectively, of said gate electrode; a source region of a second conductivity type which is in contact with said source electrode; a drain region of the second conductivity type which is in contact with said drain electrode; a punch-through stopper layer of the first conductivity type formed in contact with said source region at a location deeper than a junction between said source region of the second conductivity type and said semiconductor substrate of the first conductivity type in such a gate overlap structure that said punch-through layer penetrates from beneath an end face of said gate insulation film adjacent to said source electrode toward said drain electrode in contact with said gate insulation film; and a field relaxation layer of the second conductivity type formed in contact with said drain region in such a gate overlap structure in which said field relaxation layer penetrates from beneath an end face of said gate insulation film adjacent to said drain electrode toward said source electrode in contact with said gate insulation film; wherein a high-density layer of the second conductivity type which is in contact with said source electrode and a high-density layer of the second conductivity type which is in contact with said drain electrode are disposed at both sides, respectively, of said gate electrode without being in contact with said gate insulation film.