Patent ID: 6972459

Claim:
A metal oxide semiconductor transistor comprising: a drift layer of a first conductive type formed on a substrate, wherein the drift layer has a first epitaxial layer of a first conductive type and having a first thickness and a second epitaxial layer of a first conductive type and having a second thickness, the first thickness being greater than the second thickness; a base region of a second conductive type formed on said second epitaxial layer of said drift layer; at least one source region of the first conductive type formed in a surficial layer of said base region; at least one gate electrode facing to said base region and said source region via a gate insulating film; a source electrode in contact with said base region and said source region; and a nitrogen cluster containing layer embedded in said first epitaxial layer of said drift layer and extending under said base region so that at least a part of said first epitaxial layer of said drift layer under said nitrogen cluster containing layer is larger that a part of said first epitaxial layer of said drift layer over said nitrogen cluster containing layer.