Semiconductor device, fabrication method of the semiconductor devices

Abstract

In a semiconductor device, a YAG substrate is formed as a single-crystal substrate of any of surface orientations (100), (110), and (111). In the fabrication of the semiconductor device, a TMAl gas is first fed onto the YAG substrate so as to form a nucleation layer made of aluminum, which is a group-III element. Then, an NH 3 gas is fed onto the nucleation layer. This turns the surface of the nucleation layer into a group-V element and then forms a group-III-V compound layer of AlN. Then, a mixed gas of TMAl gas and NH 3 gas is fed onto the group-III-V compound layer so as to form another group-III-V compound layer. Finally, a group-III nitride semiconductor layer is crystal-grown on the group-III compound layer.

1 . A method for fabricating a semiconductor device, the method comprising:
 forming a buffer layer, containing a group-III-V compound, on a substrate formed of Y 3 Al 5 O 12 ; and   forming a group-III nitride semiconductor layer on the buffer layer,   wherein the forming the buffer layer includes forming a nucleation layer made of a group-III element in at least a part on the substrate.   
     
     
         2 . A method for fabricating a semiconductor device according to  claim 1 , wherein the nucleation layer is formed by supplying a first gas containing a group-III element onto the substrate. 
     
     
         3 . A method for fabricating a semiconductor device according to  claim 1 , wherein the forming a buffer layer further includes changing at least a part of the surface of the nucleation layer into a group-III-V compound by combining the at least a part of the surface of the nucleation layer with a group V element. 
     
     
         4 . A method for fabricating a semiconductor device according to  claim 3 , wherein the at least a part of the surface of the nucleation layer is changed into a group-III-V compound by supplying a second gas containing a group-V element onto the nucleation layer. 
     
     
         5 . A method for fabricating a semiconductor device according to  claim 1 , wherein the forming a buffer layer further includes forming a group-III-V compound layer on the nucleation layer. 
     
     
         6 . A method for fabricating a semiconductor device according to  claim 5 , wherein the group-III-V compound layer is formed on the nucleation layer by supplying a third gas containing both of a group-III element and a group-V element onto the nucleation layer. 
     
     
         7 . A method for fabricating a semiconductor device according to  claim 1 , wherein a nucleation layer made of one or more of Al, Ga, and In as group-III elements is formed. 
     
     
         8 . A method for fabricating a semiconductor device according to  claim 1 , further comprising forming another of the buffer layer on the buffer layer. 
     
     
         9 . A method for fabricating a semiconductor device according to  claim 1 , wherein the substrate is a single-crystal substrate of any of surface orientations (100), (110), and (111) or a polycrystalline substrate of a plurality of surface orientations. 
     
     
         10 . A method for fabricating a semiconductor device according to  claim 1 , wherein the substrate is such that part of Y is replaced by any of Lu, Sc, La, Gd, and Sm and/or part of Al is replaced by any of In, B, Tl, and Ga. 
     
     
         11 . A method for fabricating a semiconductor device according to  claim 1 , wherein the substrate contains at least one type of activator selected from the group consisting of Ce, Tb, Eu, Ba, Sr, Mg, Ca, Zn, Si, Cu, Ag, Au, Fe, Cr, Pr, Nd, Dy, Co, Ni, and Ti. 
     
     
         12 . A method for fabricating a semiconductor device according to  claim 11 , wherein the activator contains Ce 3+ . 
     
     
         13 . A method for fabricating a semiconductor device according to  claim 11 , wherein the activator contains Tb 2+ . 
     
     
         14 . A method for fabricating a semiconductor device according to  claim 11 , wherein the activator contains Eu 2+ . 
     
     
         15 . A semiconductor device comprising:
 a substrate formed of Y 3 Al 5 O 12 ; and   a buffer layer, containing a group-III-V compound, formed on the substrate; and   a group-III nitride semiconductor layer formed on the buffer layer,   the buffer layer including:   a nucleation layer, made of a group-III element, formed on the substrate; and   a group-III-V compound layer formed on the nucleation layer.