Semiconductor device

Abstract

A semiconductor device is provided. On one main surface side of an n-type semiconductor substrate, a p-type diffusion region to serve as an anode of a diode is formed. A guard ring formed of a p-type diffusion region is formed to surround the anode. On the other main surface side, an n-type ultrahigh-concentration impurity layer and an n-type high-concentration impurity layer to serve as a cathode are formed. In a guard-ring opposed region located in the cathode and opposite to the guard ring, a cathode-side p-type diffusion region is formed. Accordingly, concentration of the electric current on an outer peripheral end portion of the anode is suppressed.

1 . A semiconductor device including a diode, comprising:
 a semiconductor substrate of a first conductivity type having a first main surface and a second main surface opposite to each other;   an anode of a second conductivity type formed on said first main surface side of said semiconductor substrate;   a guard ring formed at a distance from said anode and surrounding said anode;   a cathode of the first conductivity type formed on said second main surface side of said semiconductor substrate; and   a cathode-side impurity region of the second conductivity type formed in a region located in said cathode and opposite to said guard ring.   
   
   
       2 . The semiconductor device according to  claim 1 , wherein
 said cathode-side impurity region is formed with a predetermined occupying area and a predetermined depth.   
   
   
       3 . The semiconductor device according to  claim 1 , wherein
 said cathode-side impurity region includes an extended region extended from the region located opposite to said guard ring toward a region opposite to said anode.   
   
   
       4 . The semiconductor device according to  claim 3 , wherein
 an area occupied by said extended region is set to be not more than 50% of an area occupied by said anode.   
   
   
       5 . The semiconductor device according to  claim 1 , wherein
 a heavy metal is diffused in said cathode-side impurity region.   
   
   
       6 . The semiconductor device according to  claim 1 , wherein
 a crystal defect is formed in said cathode-side impurity region.   
   
   
       7 . The semiconductor device according to  claim 1 , wherein
 said cathode-side impurity region is electrically floating with respect to an electrode on said cathode side.   
   
   
       8 . The semiconductor device according to  claim 1 , comprising a field effect transistor formed on said first main surface side of said semiconductor substrate.