Abstract: A semiconductor device includes a metal film, not in ohmic contact with a guard ring region (a second region). The metal film is formed on that surface portion of an insulating film under which the guard ring region is formed to surround a base region (a first region) of a planar transistor. In this arrangement, a planar semiconductor device with a high withstand voltage, which is free of short-circuiting between electrodes upon the measurement of the withstand voltage and involves no degeneration of the withstand voltage resulting from an atmospheric humidity, can be obtained. The metal film, which is not in contact with the guard ring region, is "electrically floated", i.e., is not in contact with any area inclusive of the guard ring region.

Abstract: A junction type field effect transistor comprises a semiconductor layer of one conductivity type acting as a drain region, a source region of said one conductivity type formed to a prescribed depth from the surface of the semiconductor layer, an insulation layer formed to a prescribed depth from the surface of the semiconductor layer to surround the source region, and a gate region of the opposite conductivity type formed in the proximity of the sorce region. The insulation layer and source region are formed to substantially the same depth.