Enhancement-type semiconductor having reduced leakage current

A semiconductor device comprising:

• a semiconductor region of a first conductivity type;
• a gate electrode disposed on said semiconductor region with a gate insulation film interposed therebetween;
• a source region and a drain region, each being a second conductivity type, disposed at a surface portion of said semiconductor region, whereby a channel region is defined at said surface portion of said semiconductor region between said drain region and said source region below said gate electrode;
• and
• a high-concentration region of said first conductivity type disposed overlapping with said channel region and having an impurity concentration higher than an impurity concentration of said surface portion of said semiconductor region,
• wherein said high-concentration region is disposed remotely from both said source region and said drain region, and an end portion thereof is located at a position where an electrical field within a depletion layer which extends within said semiconductor region from a PN junction between said drain region and said semiconductor region toward said high-concentration region does not become the critical field causing an avalanche breakdown or a Zener breakdown when a rated voltage is applied between said drain region and said semiconductor region.