Semiconductor device

Abstract

According to one embodiment, a semiconductor device includes a first semiconductor region, a second semiconductor region, a third semiconductor region, an insulating film, and a control electrode. The first semiconductor region includes a silicon carbide of a first conductivity type. The second semiconductor region is provided on the first semiconductor region, includes a silicon carbide of a second conductivity type, and has a first main surface. The third semiconductor region is provided on the second semiconductor region and includes the silicon carbide of the first conductivity type. The film is provided on the surface. The electrode is provided on the film, and has a first region close to the third semiconductor region side, and a second region closer to the first semiconductor region side than the first region. An effective work function of is the first region is larger than an effective work function of the second region.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a first semiconductor region including a silicon carbide of a first conductivity type;   a second semiconductor region provided on the first semiconductor region, the second semiconductor region including a silicon carbide of a second conductivity type, the second semiconductor region having a first main surface;   a third semiconductor region provided on the second semiconductor region, the third semiconductor region including the silicon carbide of the first conductivity type;   an insulating film provided at least on the first main surface of the second semiconductor region; and   a control electrode provided on the insulating film, the control electrode having a first region close to the third semiconductor region side, and a second region closer to the first semiconductor region side than the first region,   an effective work function of the first region being larger than an effective work function of the second region.   
     
     
         2 . The device according to  claim 1 , wherein the first region and the second region are provided in an boundary face side between the control electrode and the insulating film. 
     
     
         3 . The device according to  claim 2 , wherein the control electrode includes a third region provided in an opposite side to the insulating film in the first region and the second region. 
     
     
         4 . The device according to  claim 3 , wherein an electric resistance value of the third region is smaller than an electric resistance value of the first region and an electric resistance value of the second region. 
     
     
         5 . The device according to  claim 1 , wherein the first region and the second region include a polysilicon, the polysilicon added an impurity. 
     
     
         6 . The device according to  claim 5 , wherein the first region is a second conductivity type and the second region is a first conductivity type. 
     
     
         7 . The device according to  claim 1 , wherein
 the first region is adjacent to the second region in a first direction, the first direction connecting the first semiconductor region and the third semiconductor region, and being along the first main surface, and   a boundary position between the first region and the second region is provided at a position overlapping the first main surface as view in a direction being orthogonal to the first main surface.   
     
     
         8 . The device according to  claim 7 , wherein in the case of setting a length in the first direction of the first main surface on the basis of an end portion in an opposite side to the third semiconductor region of the first main surface to L, and a distance in the first direction of the boundary position on the basis of the end portion to X, X/L is not less than 0 and less than 0.5. 
     
     
         9 . The device according to  claim 1 , wherein the insulating film includes a silicon oxide added a nitrogen. 
     
     
         10 . The device according to  claim 1 , wherein a composition of an element included in the first region is different from a composition of an element included in the second region. 
     
     
         11 . The device according to  claim 1 , further comprising a fourth semiconductor region including the silicon carbide of the first conductivity type,
 the fourth semiconductor region provided in a direction orthogonal to the first main surface so as to be spaced from the second semiconductor region.   
     
     
         12 . The device according to  claim 1 , further comprising a fourth semiconductor region including the silicon carbide of the first conductivity type,
 the fourth semiconductor region provided in a direction along the first main surface so as to be spaced from the second semiconductor region.   
     
     
         13 . The device according to  claim 1 , further comprising:
 a fourth semiconductor region contacting with the first semiconductor region, the fourth semiconductor region including the silicon carbide of the first conductivity type;   a first electrode electrically connected with the third semiconductor region; and   a second electrode electrically connected with the fourth semiconductor region.   
     
     
         14 . The device according to  claim 1 , further comprising:
 a substrate provided between the first semiconductor region and the second electrode, the substrate including the silicon carbide.   
     
     
         15 . The device according to  claim 14 , wherein the substrate has a conductivity type of the first conductivity type. 
     
     
         16 . The device according to  claim 14 , wherein the substrate has a conductivity type of the second conductivity type. 
     
     
         17 . A semiconductor device comprising:
 a first semiconductor region including a silicon carbide of a first conductivity type;   a second semiconductor region provided on the first semiconductor region, the second semiconductor region including a silicon carbide of a second conductor type and the second semiconductor region having a first main surface;   a third semiconductor region provided on the second semiconductor region, the third semiconductor region including the silicon carbide of the first conductivity type;   an insulating film provided at least on the first main surface of the second semiconductor region and includes a metal oxide layer; and   a control electrode provided on the insulating film,   the metal oxide layer has a first region close to the third semiconductor region side, and a second region closer to the first semiconductor region side than the first region, and   an effective work function of the first region being larger than an effective work function of the second region.   
     
     
         18 . The device according to  claim 17 , wherein
 the insulating film includes a first layer provided between the first main surface and the metal oxide layer, and   the first layer includes a silicon oxide added a nitrogen.   
     
     
         19 . The device according to  claim 17 , wherein
 the first region is adjacent to the second region in a first direction, the first direction connecting the first semiconductor region and the third semiconductor region, and being along the first main surface, and   a boundary position between the first region and the second region is provided at a position overlapping the first main surface as view in a direction orthogonal to the first main face.   
     
     
         20 . The device according to  claim 17 , wherein in the case of setting a length in the first direction of the first main surface on the basis of an end portion in an opposite side to the third semiconductor region of the first main surface to L, and a distance in the first direction of the boundary position on the basis of the end portion to X, X/L is not less than 0 and less than 0.5.