Semiconductor device

Abstract

A semiconductor device including a first nitride semiconductor layer formed over a substrate, a second nitride semiconductor layer formed on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer, a trench penetrating through the second nitride semiconductor layer to reach the middle of the first nitride semiconductor layer, a conductive film formed at a corner portion corresponding to an end portion of a bottom surface of the trench and a gate electrode disposed via a gate insulating film inside the trench including a region on the conductive film.

What is claimed is: 
     
         1 . A semiconductor device including:
 a first nitride semiconductor layer formed over a substrate;   a second nitride semiconductor layer formed on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer;   a trench penetrating through the second nitride semiconductor layer to reach the middle of the first nitride semiconductor layer;   a conductive film formed at a corner portion corresponding to an end portion of a bottom surface of the trench; and   a gate electrode disposed via a gate insulating film inside the trench including a region on the conductive film.   
     
     
         2 . The semiconductor device according to  claim 1 ,
 wherein the conductive film has a first portion disposed along a side surface of the trench from the corner portion and a second portion disposed along the bottom surface of the trench from the corner portion.   
     
     
         3 . The semiconductor device according to  claim 2 ,
 wherein a height of the first portion is higher than an interface between the first nitride semiconductor layer and the second nitride semiconductor layer.   
     
     
         4 . The semiconductor device according to  claim 2 ,
 wherein a height of the first portion is equal to or lower than an interface between the first nitride semiconductor layer and the second nitride semiconductor layer.   
     
     
         5 . The semiconductor device according to  claim 2 ,
 wherein a length of the second portion is larger than a film thickness of the first portion.   
     
     
         6 . The semiconductor device according to  claim 2 ,
 wherein the second portion extends from a sidewall of the trench to inside of a sidewall of the gate electrode.   
     
     
         7 . The semiconductor device according to  claim 1 ,
 wherein the conductive film is formed in a sidewall shape so as to be in contact with a sidewall of the trench.   
     
     
         8 . A semiconductor device including:
 a first nitride semiconductor layer formed over a substrate;   a second nitride semiconductor layer formed on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer;   a trench penetrating through the second nitride semiconductor layer to reach the middle of the first nitride semiconductor layer;   a third nitride semiconductor layer formed at a corner portion corresponding to an end portion of a bottom surface of the trench and having a band gap wider than that of the first nitride semiconductor layer; and   a gate electrode disposed via a gate insulating film inside the trench including a region on the third nitride semiconductor layer.   
     
     
         9 . The semiconductor device according to  claim 8 ,
 wherein the conductive film has a first portion disposed along a side surface of the trench from the corner portion and a second portion disposed along the bottom surface of the trench from the corner portion.   
     
     
         10 . The semiconductor device according to  claim 9 ,
 wherein a height of the first portion is higher than an interface between the first nitride semiconductor layer and the second nitride semiconductor layer.   
     
     
         11 . The semiconductor device according to  claim 9 ,
 wherein a height of the first portion is equal to or lower than an interface between the first nitride semiconductor layer and the second nitride semiconductor layer.   
     
     
         12 . The semiconductor device according to  claim 9 ,
 wherein a length of the second portion is larger than a film thickness of the first portion.   
     
     
         13 . The semiconductor device according to  claim 9 ,
 wherein the second portion extends from a sidewall of the trench to inside of a sidewall of the gate electrode.   
     
     
         14 . The semiconductor device according to  claim 8 ,
 wherein the conductive film is formed in a sidewall shape so as to be in contact with a sidewall of the trench.   
     
     
         15 . A manufacturing method of a semiconductor device including:
 forming a stacked body by forming a first nitride semiconductor layer and a second nitride semiconductor layer having a band gap wider than that of the first nitride semiconductor layer on the first nitride semiconductor layer;   forming a trench penetrating through the second nitride semiconductor layer to reach the middle of the first nitride semiconductor layer by etching the stacked body;   forming a conductive film over the stacked body including inside of the trench;   etching the conductive film to leave the conductive film at a corner portion corresponding to an end portion of a bottom surface of the trench;   forming a gate insulating film inside the trench including a region on the conductive film; and   forming a gate electrode on the gate insulating film.   
     
     
         16 . The manufacturing method of a semiconductor device according to  claim 15 ,
 wherein the etching the conductive film includes:   forming a mask film on the conductive film and anisotropically etching the mask film, thereby forming a sidewall film on a sidewall portion of the trench via the conductive film;   etching the conductive film with using the sidewall film as a mask; and   removing the sidewall film.   
     
     
         17 . The manufacturing method of a semiconductor device according to  claim 16 ,
 wherein a height of the sidewall film is higher than an interface between the first nitride semiconductor layer and the second nitride semiconductor layer.   
     
     
         18 . The manufacturing method of a semiconductor device according to  claim 16 ,
 wherein a height of the sidewall film is equal to or lower than an interface between the first nitride semiconductor layer and the second nitride semiconductor layer.