Dielectric isolation type semiconductor device and method for manufacturing the same

Abstract

A dielectric isolation type semiconductor device and a manufacturing method therefor achieve high dielectric resistance while preventing the dielectric strength of the semiconductor device from being limited depending on the thickness of a dielectric layer and the thickness of a first semiconductor layer. A semiconductor substrate () and an ntype semiconductor layer () are bonded to each other through a buried oxide film layer (). A first porous oxide film area () is formed in the semiconductor substrate in a state contacting with the buried oxide film layer. A power device is formed on the ntype semiconductor layer. The first porous oxide film area is formed in an area including a location right under a first main electrode () and extending from the first main electrode side up to a range of more than 40% of a distance (L) between the first and second main electrodes ().