Semiconductor device and method for fabricating the same

Abstract

There is provided a semiconductor device and a method for fabricating the same whose withstanding characteristic may be enhanced and whose ON resistance may be reduced. A MIS-type HEMT includes a carrier traveling layer made of a group-III nitride semiconductor and formed on a supporting substrate, a carrier supplying layer made of a group-III nitride semiconductor and formed on the carrier traveling layer, source and drain electrodes formed on the carrier supplying layer, insulating films formed on the carrier supplying layer and a gate electrode formed on the insulating films. The insulating film is formed in a region interposed between the source and drain electrodes and has a trench whose cross-section is inverted trapezoidal and whose upper opening is wider than a bottom thereof. The gate electrode is formed at least from the bottom of the trench onto the insulating films on the side of the drain electrode.

1 . A method for fabricating a semiconductor device, comprising steps of:
 forming an insulating film having a first trench on a carrier supplying layer of a supporting substrate having a carrier traveling layer, the carrier supplying layer formed on the carrier traveling layer and source and drain electrodes that ohmically contact with the carrier traveling layer; and   forming a gate electrode at least from a bottom of the first trench onto the insulating film on the side of the drain electrode;   wherein the first trench is formed in a region interposed between the source and drain electrodes so as to have a shape whose cross-section is inverted trapezoidal in which an upper opening is wider than a bottom thereof.   
     
     
         2 . The method according to  claim 1 , wherein the insulating film forming step comprises steps of:
 forming a first insulating film on the carrier supplying layer;   forming an aperture that exposes the carrier supplying layer in the first insulating film interposed between the source and drain electrodes; and   forming a second insulating film that covers the first insulating film and a surface of the aperture;   wherein the first trench is formed so that it becomes a trench formed by the surface of the second insulating film formed within the aperture.   
     
     
         3 . The method according to  claim 1 , wherein the insulating film forming step comprises steps of:
 forming a first insulating film on the carrier supplying layer;   forming a second insulating film on the first insulating film; and   forming an aperture that exposes the first insulating film in the second insulating film between the source and drain electrodes;   wherein the first trench is formed so that it becomes a trench formed by side surfaces and an upper surface of the first insulating film within the aperture.   
     
     
         4 . The method according to  claim 1 , wherein the first trench is formed by removing at least part of the insulating film by wet etching. 
     
     
         5 . The method according to  claim 2 , wherein the first trench is formed by removing at least part of the insulating film by wet etching. 
     
     
         6 . The method according to  claim 3 , wherein the first trench is formed by removing at least part of the insulating film by wet etching. 
     
     
         7 . The method according to  claim 4 , wherein the insulating film forming step includes a step of forming a second trench that reaches to an upper part of the carrier traveling layer itself under the aperture formed in the aperture forming step; and
 an under part of the first trench itself is composed of the second trench.   
     
     
         8 . The method according to  claim 5 , wherein the insulating film forming step includes a step of forming a second trench that reaches to an upper part of the carrier traveling layer itself under the aperture formed in the aperture forming step; and
 an under part of the first trench itself is composed of the second trench.   
     
     
         9 . The method according to  claim 6 , wherein the insulating film forming step includes a step of forming a second trench that reaches to an upper part of the carrier traveling layer itself under the aperture formed in the aperture forming step; and
 an under part of the first trench itself is composed of the second trench.