P-fet with graded silicon-germanium channel

Abstract

A method of forming a semiconductor structure includes etching a semiconductor region of a substrate to form a thinned semiconductor region, and forming a silicon-germanium layer on the thinned semiconductor region, the silicon-germanium layer having a graded concentration profile of germanium atoms.

What is claimed is: 
     
         1 . A method of forming a semiconductor structure, the method comprising:
 etching a semiconductor region of a substrate to form a thinned semiconductor region; and   forming a silicon-germanium layer on the thinned semiconductor region, the silicon-germanium layer having a graded concentration profile of germanium atoms.   
     
     
         2 . The method of  claim 1 , wherein the thinned semiconductor region comprises a thinned silicon fin or a thinned silicon ETSOI layer. 
     
     
         3 . The method of  claim 1 , wherein forming the silicon-germanium layer comprises epitaxially growing the silicon-germanium layer on opposite sidewalls of the thinned silicon fin to form a graded silicon-germanium fin. 
     
     
         4 . The method of  claim 1 , wherein forming the silicon-germanium layer comprises epitaxially growing the silicon-germanium layer above and in direct contact with a top surface of the thinned silicon ETSOI layer to form a graded ETSOI layer. 
     
     
         5 . The method of  claim 1 , wherein the graded concentration profile of germanium atoms is achieved by varying an amount of germanium atoms in a source gas during epitaxial growth of the silicon-germanium layer. 
     
     
         6 . A method of forming a semiconductor structure, the method comprising:
 forming a silicon fin on a semiconductor substrate;   etching the silicon fin to substantially reduce a width of the silicon fin; and   forming a silicon-germanium layer on opposite sidewalls of the etched silicon fin to form a silicon-germanium fin, wherein a concentration of germanium atoms in the silicon-germanium fin continuously increases from a center of the silicon-germanium fin to outer edges of the silicon-germanium fin.   
     
     
         7 . The method of  claim 6 , wherein forming the silicon-germanium layer comprises epitaxially growing the silicon-germanium layer with a layered germanium concentration profile. 
     
     
         8 . The method of  claim 7 , wherein epitaxially growing the silicon-germanium layer with the layered germanium concentration profile comprises varying an amount of germanium atoms in a source gas during epitaxial growth of the silicon-germanium layer to form a graded silicon-germanium layer. 
     
     
         9 . The method of  claim 8 , wherein the graded silicon-germanium layer comprises a plurality of sub-layers, each sub-layer in the plurality of sub-layers has an increasing concentration of germanium atoms. 
     
     
         10 . The method of  claim 6 , wherein the concentration of germanium atoms in the silicon-germanium fin continuously increasing from a center of the silicon-germanium fin to outer edges of the silicon-germanium fin allows holes to be substantially near a subsequently formed gate structure.