Patent ID: 8410550

Claim:
A semiconductor device comprising: a semiconductor substrate having a first region of a first conductivity type; a gate insulating film formed on said semiconductor substrate and above said first region; a gate electrode formed on said gate insulating film; a source region of a second conductivity type opposite to said first conductivity type formed in said semiconductor substrate, above said first region and below one side of said gate electrode; a first low concentration drain region of said second conductivity type formed in said semiconductor substrate, located above said first region and below another side of said gate electrode, and including a first end which is opposite to a side of said source region and which is located under said gate electrode; a high concentration drain region of said second conductivity type formed in said semiconductor substrate, located above said first region, on said first low concentration drain region and apart from said gate electrode, an impurity concentration of said high concentration drain region being higher than an impurity concentration of said first low concentration drain region; and an opposite conductivity type region of said first conductivity type formed in said semiconductor substrate, located on a part of said first low concentration drain region and between said high concentration drain region and said first low concentration region, a part of said opposite conductivity type region being located at a surface of said semiconductor surface, said opposite conductivity type region and said first low concentration drain region forming a pn junction, said opposite conductivity type region and said high concentration drain region forming a pn junction, an impurity concentration of said opposite conductivity type region being higher than said impurity concentration of said first low concentration drain region, and lower than said impurity concentration of said high concentration drain region and said opposite conductivity type region including a second end which is opposite to said source region and which is located under said gate electrode.