Mos device using accumulation layer as channel

Claim 1

A semiconductor device comprising: a drain region made of one conductivity type semiconductor substrate and having first and second major surfaces; a drain electrode for forming an ohmic contact with said drain region, and located on said second major surface of said drain region; first and second grooves, each having a U-shape and dug from said first major surface of said drain region; a gate electrode covered with an insulating film and formed in said first groove; a source electrode metal embedded in said second groove, for forming a Schottky junction with said drain region; a source region made of the same conductivity type semiconductor as that of said drain region, formed at said first major surface of said drain region, and being in contact with said source electrode metal at one side thereof and with said insulating film at the other side thereof; a channel region corresponding to a portion of said drain region, being in contact with said source region, and being sandwiched by said source electrode and said gate electrode covered with the insulating film, said channel region being depleted by both a difference in work functions between the materials of said gate electrode and of said drain region, and also said Schottky junction, when at least a potential of said gate electrode is equal to a potential of said source electrode; wherein a ratio of a channel length to a channel thickness is set to such a value that said channel region is not brought into an open state even when the electric potential of said gate electrode is substantially equal to the electric potential of said source electrode, and the electric potential of said drain electrode is substantially equal to a breakdown voltage of said semiconductor device, said channel length being defined by a distance from a first boundary plane between said source region and said channel region to the bottom of said second groove for embedding said source electrode, and measured along the side wall of said second groove, and said channel thickness being defined by a distance from a second boundary plane between said source electrode metal and said channel region to a third boundary plane between said insulating film and said channel region, and measured along said first major surface of said drain region.