Semiconductor device

Abstract

A semiconductor device includes a first semiconductor layer of a first conductivity type formed on one side of a semiconductor substrate; a second semiconductor layer of a second conductivity type formed on the first semiconductor layer; a third semiconductor layer of the first conductivity type formed on the second semiconductor layer; an opening part formed by removing part of the first to third semiconductor layers; a gate insulating film formed so as to cover an inner wall of the opening part; a gate electrode formed inside the opening part via the gate insulating film; a source electrode formed on a surface of the third semiconductor layer; a drain electrode connected to a part corresponding to the gate electrode on another side of the semiconductor substrate; and a fourth electrode formed on the another side of the semiconductor substrate at a part corresponding to the source electrode.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a first semiconductor layer of a first conductivity type formed on one side of a semiconductor substrate having conductivity;   a second semiconductor layer of a second conductivity type formed on the first semiconductor layer;   a third semiconductor layer of the first conductivity type formed on the second semiconductor layer;   an opening part formed by removing part of the third semiconductor layer, the second semiconductor layer, and the first semiconductor layer;   a gate insulating film formed so as to cover an inner wall of the opening part;   a gate electrode formed inside the opening part via the gate insulating film;   a source electrode formed on a surface of the third semiconductor layer;   a drain electrode connected to a part corresponding to the gate electrode on another side of the semiconductor substrate; and   a fourth electrode formed on the another side of the semiconductor substrate at a part corresponding to the source electrode.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein
 the fourth electrode is formed on a back side insulating film which is formed on the another side of the semiconductor substrate.   
     
     
         3 . A semiconductor device comprising:
 a first semiconductor layer of a first conductivity type formed on one side of a semiconductor substrate having conductivity;   a second semiconductor layer of a second conductivity type formed on the first semiconductor layer;   a third semiconductor layer of the first conductivity type formed on the second semiconductor layer;   an opening part formed by removing part of the third semiconductor layer, the second semiconductor layer, and the first semiconductor layer;   a gate insulating film formed so as to cover an inner wall of the opening part;   a gate electrode formed inside the opening part via the gate insulating film;   a source electrode formed on a surface of the third semiconductor layer;   a back side removal area formed by removing, from another side of the semiconductor substrate, part of the semiconductor substrate and the first semiconductor layer at a part corresponding to the source electrode;   a fourth electrode formed in the back side removal area where the first semiconductor layer is exposed; and   a drain electrode connected to a part corresponding to the gate electrode on the another side of the semiconductor substrate.   
     
     
         4 . The semiconductor device according to  claim 3 , wherein
 the fourth electrode is formed on a back side insulating film where the first semiconductor layer is exposed.   
     
     
         5 . The semiconductor device according to  claim 1 , wherein
 a potential applied to the fourth electrode is between a potential applied to the drain electrode and a potential applied to the source electrode.   
     
     
         6 . The semiconductor device according to  claim 1 , wherein
 a potential applied to the fourth electrode is a potential applied to the source electrode or a potential applied to the gate electrode.   
     
     
         7 . The semiconductor device according to  claim 1 , wherein
 an insulating film is formed between the drain electrode and the fourth electrode.   
     
     
         8 . A semiconductor device comprising:
 a first semiconductor layer of a first conductivity type formed on one side of a semiconductor substrate having conductivity;   a second semiconductor layer of a second conductivity type formed on the first semiconductor layer;   a third semiconductor layer of the first conductivity type formed on the second semiconductor layer;   an opening part formed by removing part of the third semiconductor layer, the second semiconductor layer, and the first semiconductor layer;   a gate insulating film formed so as to cover an inner wall of the opening part;   a gate electrode formed inside the opening part via the gate insulating film;   a source electrode formed on a surface of the third semiconductor layer; and   a drain electrode connected to a part corresponding to the gate electrode, and not connected to a part corresponding to the source electrode, on another side of the semiconductor substrate.   
     
     
         9 . The semiconductor device according to  claim 8 , wherein
 a back side insulating film is formed at a part corresponding to the source electrode on the another side of the semiconductor substrate.   
     
     
         10 . A semiconductor device comprising:
 a first semiconductor layer of a first conductivity type formed on one side of a semiconductor substrate having conductivity;   a second semiconductor layer of a second conductivity type formed on the first semiconductor layer;   a third semiconductor layer of the first conductivity type formed on the second semiconductor layer;   an opening part formed by removing part of the third semiconductor layer, the second semiconductor layer, and the first semiconductor layer;   a gate insulating film formed so as to cover an inner wall of the opening part;   a gate electrode formed inside the opening part via the gate insulating film;   a source electrode formed on a surface of the third semiconductor layer;   a back side removal area formed by removing, from another side of the semiconductor substrate, part of the semiconductor substrate and the first semiconductor layer at a part corresponding to the source electrode; and   a drain electrode connected to a part corresponding to the gate electrode on the another side of the semiconductor substrate.   
     
     
         11 . The semiconductor device according to  claim 10  wherein
 a back side insulating film is formed in the back side removal area where the first semiconductor layer is exposed. 
 
     
     
         12 . The semiconductor device according to  claim 1  wherein
 the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer are formed with a material including GaN.