Semisonductor device

Abstract

A semiconductor device includes an AlGaN film formed on a GaN film on a substrate, a gate electrode formed on the AlGaN film, and source and drain electrodes formed on either side of the gate electrode on the AlGaN film. An n-type In x Ga y Al 1-x-y N film is interposed between the source and drain electrodes and the AlGaN film. Alternatively, the semiconductor device includes an n-type In x Ga y Al 1-x-y N film formed on a GaN film on a substrate, a gate electrode formed on the In x Ga y Al 1-x-y N film, and source and drain electrodes formed on either side of the gate electrode on the In x Ga y Al 1-x-y N film.

1 . A semiconductor device, comprising: 
 a GaN film formed on a substrate;    an AlGaN film formed on the GaN film;    a gate electrode formed on the AlGaN film; and    source and drain electrodes formed on either side of the gate electrode on the AlGaN film;    wherein an n-type In x Ga y Al 1-x-y N film (wherein 0<x<1, 0≦y<1, 0<x+y<1) is formed between the source and drain electrodes and the AlGaN film.    
   
   
       2 . The semiconductor device according to  claim 1 , wherein the composition of the In x Ga y Al 1-x-y N film is set so that the lattice constant of the In x Ga y Al 1-x-y N film and the lattice constant of the GaN film are substantially matching, and polarization occurring in the In x Ga y Al 1-x-y N film is equal to or larger than polarization occurring in the AlGaN film.  
   
   
       3 . The semiconductor device according to  claim 1 , wherein an InGaN film, or a layered film of an InGaN film and another GaN film, is formed between the GaN film and the AlGaN film.  
   
   
       4 . A semiconductor device, comprising: 
 a GaN film formed on a substrate;    an n-type In x Ga y Al 1-x-y N film (wherein 0<x<1, 0≦y<1, 0<x+y<1) formed on the GaN film;    a gate electrode formed on the In x Ga y Al 1-x-y N film; and    source and drain electrodes formed on either side of the gate electrode on the In x Ga y Al 1-x-y N film.    
   
   
       5 . The semiconductor device according to  claim 4 , wherein the composition of the In x Ga y Al 1-x-y N film is set so that the lattice constant of the In x Ga y Al 1-x-y N film and the lattice constant of the GaN film are substantially matching.  
   
   
       6 . The semiconductor device according to  claim 4 , wherein an InGaN film, or a layered film of an InGaN film and another GaN film, is formed between the GaN film and the In x Ga y Al 1-x-y N film.