Semiconductor device having a gate insulating film having a high dielectric constant portion for relaxing an electric field generated in the gate insulating film

Abstract

A method for producing a semiconductor power device, includes forming a gate trench from a surface of a semiconductor layer toward an inside thereof. A first insulation film is formed on an inner surface of the gate trench. The method also includes removing a part on a bottom surface of the gate trench in the first insulation film. A second insulation film having a dielectric constant higher than SiO2 is formed in such a way as to cover the bottom surface of the gate trench exposed by removing the first insulation film.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a semiconductor layer of a first conductivity type;   body regions of a second conductivity type plurally formed on a surface layer portion of the semiconductor layer at intervals;   a source region of the first conductivity type formed on a surface layer portion of each body region;   a gate insulating film provided on the semiconductor layer to extend between the body regions adjacent to each other;   a gate electrode provided on the gate insulating film and opposed to the body regions; and   a protrusion projected from the surface of the semiconductor layer such that the protrusion is raised with respect to the surface of the semiconductor layer between the body regions adjacent to each other.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the gate insulating film includes a first portion being in contact with the protrusion, the first portion having a thickness thinner than a thickness of a remaining portion of the gate insulating film. 
     
     
         3 . The semiconductor device according to  claim 2 , wherein the gate insulating film includes a second portion being in contact with the body regions, the second portion having a thickness thicker than the thickness of the first portion. 
     
     
         4 . The semiconductor device according to  claim 1 , comprising an insulating film formed on the gate electrode such that the gate electrode is covered with the insulating film. 
     
     
         5 . The semiconductor device according to  claim 4 , comprising an electrode formed on the insulating film. 
     
     
         6 . The semiconductor device according to  claim 4 , wherein the insulating film has a shape conformal to an outer shape of the gate electrode. 
     
     
         7 . The semiconductor device according to  claim 6 , wherein the electrode has a shape conformal to an outer shape of the insulating film. 
     
     
         8 . The semiconductor device according to  claim 1 , comprising a body contact region formed on the surface layer portion of each body region. 
     
     
         9 . The semiconductor device according to  claim 8 , wherein the body contact region is deeper than the source region. 
     
     
         10 . The semiconductor device according to  claim 1 , wherein the protrusion has a second conductivity type. 
     
     
         11 . The semiconductor device according to  claim 10 , wherein the protrusion is formed by implanting at least one of Al or B as a second conductivity type impurity. 
     
     
         12 . The semiconductor device according to  claim 1 , wherein the semiconductor layer is made of SiC. 
     
     
         13 . The semiconductor device according to  claim 1 , wherein the gate electrode is formed in a latticed manner. 
     
     
         14 . The semiconductor device according to  claim 1 , wherein an end of the protrusion is substantially continuous to an end of each body region. 
     
     
         15 . The semiconductor device according to  claim 1 , wherein the semiconductor layer has a dielectric breakdown field of not less than 1 MV/cm. 
     
     
         16 . The semiconductor device according to  claim 1 , wherein the protrusion includes a field relaxation portion. 
     
     
         17 . The semiconductor device according to  claim 1 , wherein the gate insulating film provided on the semiconductor layer overlaps the body regions adjacent to each other.