Semiconductor device and method for fabricating the same

Abstract

The semiconductor device comprises a semiconductor layer 18 formed on an insulation layer 16, a gate electrode 22 formed on the semiconductor layer with a gate insulation film 20 formed therebetween, a source/drain region 24 formed on the semiconductor layer on both sides of the gate electrode, and a semiconductor region 14 buried in the insulation layer 16 in a region below the gate electrode. The surface scattering of the carriers and phonon scattering can be prevented while suppressing the short channel effect. Resultantly the semiconductor device can have high mobility and high speed.

1 . A method for fabricating a semiconductor device comprising the steps of: 
 forming a mask on a first semiconductor layer formed over a substrate;    oxidizing the first semiconductor layer on both sides of the mask to thereby form the first semiconductor layer outside the mask into an insulation layer;    forming a second semiconductor layer on the first semiconductor layer and the insulation layer;    forming a gate insulation film over the second semiconductor layer;    forming a gate electrode over the gate insulation film; and    forming a source/drain region in the second semiconductor layer on both sides of the gate electrode,    wherein the first semiconductor layer is formed of Si 1-x Ge x  where a composition ratio X is 0<X≦1, and    the second semiconductor layer is formed of Si 1-x Ge x  where a composition ratio X is 0<X≦1.    
   
   
       2 . A method for fabricating a semiconductor device according to  claim 1 , wherein the composition ratio X of the Ge of the second semiconductor layer is larger than the composition ratio X of the Ge of the first semiconductor layer.  
   
   
       3 . A method for fabricating a semiconductor device according to  claim 1 , wherein in the step of forming the source/drain region, a metal is buried in the second semiconductor layer on both sides of the gate electrode to thereby form the source/drain region of the metal.  
   
   
       4 . A method for fabricating a semiconductor device according to  claim 1 , wherein in the step of forming the source/drain region, the source/drain region is formed of a metal silicide.  
   
   
       5 . A method for fabricating a semiconductor device comprising the steps of: 
 forming a mask on a first semiconductor layer formed over a substrate;    oxidizing the first semiconductor layer on both sides of the mask to thereby form the first semiconductor layer outside the mask into an insulation layer;    forming a second semiconductor layer on the first semiconductor layer and the insulation layer;    forming a gate insulation film over the second semiconductor layer;    forming a gate electrode over the gate insulation film; and    forming a source/drain region in the second semiconductor layer on both sides of the gate electrode;    wherein    the first semiconductor region is formed of Si 1-x Ge x  where a composition ratio X is 0<X≦1, and    the second semiconductor layer is formed of Si.    
   
   
       6 . A method for fabricating a semiconductor device according to  claim 5 , wherein in the step of forming the source/drain region, a metal is buried in the second semiconductor layer on both sides of the gate electrode to thereby form the source/drain region of the metal.  
   
   
       7 . A method for fabricating a semiconductor device according to  claim 5 , wherein in the step of forming the source/drain region, the source/drain region is formed of a metal silicide.  
   
   
       8 . A method for fabricating a semiconductor device according to  claim 5 , further comprising the step of forming a third semiconductor layer on the second semiconductor layer after the step of forming the second semiconductor layer and before the step of forming the gate insulation film.  
   
   
       9 . A method for fabricating a semiconductor device according to  claim 8 , wherein the third semiconductor layer is formed of Si 1-x Ge x  where a composition ratio X is 0<X≦1.  
   
   
       10 . A method for fabricating a semiconductor device comprising the steps of: 
 forming a mask on a first semiconductor layer formed over a substrate;    oxidizing the first semiconductor layer on both sides of the mask to thereby form the first semiconductor layer outside the mask into an insulation layer;    forming a second semiconductor layer on the first semiconductor layer and the insulation layer;    forming a gate insulation film over the second semiconductor layer;    forming a gate electrode over the gate insulation film; and    forming a source/drain region in the second semiconductor layer on both sides of the gate electrode;    wherein the first semiconductor layer is formed of an intrinsic semiconductor, and    the second semiconductor layer is formed of an n type semiconductor or a p type semiconductor.    
   
   
       11 . A method for fabricating a semiconductor device comprising the steps of: 
 forming a mask on a first semiconductor layer formed over a substrate;    oxidizing the first semiconductor layer on both sides of the mask to thereby form the first semiconductor layer outside the mask into an insulation layer;    forming a second semiconductor layer on the first semiconductor layer and the insulation layer;    forming a gate insulation film over the second semiconductor layer;    forming a gate electrode over the gate insulation film; and    forming a source/drain region in the second semiconductor layer on both sides of the gate electrode;    wherein 
 the first semiconductor layer is formed of an intrinsic semiconductor, and  
 the second semiconductor layer is formed of an intrinsic semiconductor.