Method to improve transistor tox using si recessing with no additional masking steps

Abstract

A method of forming a transistor device is provided wherein a gate structure is formed over a semiconductor body of a first conductivity type. The gate structure is formed comprising a protective cap thereover and defining source/drain regions laterally adjacent thereto. A first implant is performed of a second conductivity type into both the gate structure and the source/drain regions. The semiconductor body is etched to form recesses substantially aligned to the gate structure wherein the first implant is removed from the source/drain regions. Source/drain regions are implanted or grown by a selective epitaxial growth.

1 . A method of forming a transistor device, comprising:
 forming a gate structure over a semiconductor body of a first conductivity type wherein the gate structure comprises a protective cap thereover and defines source/drain regions laterally adjacent thereto;   performing a first implant of a second conductivity type into the gate structure thru the protective cap and into source/drain regions;   etching into the semiconductor body to form recesses substantially aligned to the gate structure wherein dopant of the first implant is substantially removed from the source/drain regions;   removing the protective cap; and   performing a second implant of the second conductivity type into the source/drain regions and the gate structure.   
     
     
         2 . The method of  claim 1 , wherein forming the gate structure comprises:
 forming a gate oxide over the semiconductor body; and   depositing and patterning a conductive layer to form a gate electrode over the gate oxide.   
     
     
         3 . The method of  claim 1 , further comprising:
 forming extension regions of the second conductivity type adjacent to the gate structure, wherein performing the first implant is distinct from forming said extension regions; and   forming sidewall spacers adjacent to the gate structure.   
     
     
         4 . The method of  claim 1 , wherein the second implant is a lesser energy dose implant than the first implant dose and wherein the first implant dose is a high energy dose compared to the second implant. 
     
     
         5 . The method of  claim 1 , wherein the first implant and the second implant comprise performing at least one angled implant. 
     
     
         6 . The method of  claim 1 , wherein the recesses are less than about 200 angstroms in depth. 
     
     
         7 . The method of  claim 1 , wherein the protective cap comprises a nitride and wherein etching into the semiconductor body to form recesses removes all of the first source/drain implant. 
     
     
         8 . A method of forming a transistor device, comprising:
 forming a gate structure over a semiconductor body of a first conductivity type wherein the gate structure comprises a protective cap thereover and defines source/drain regions laterally adjacent thereto;   performing a source/drain implant of a second conductivity type into the gate structure thru the protective cap and into the source/drain regions; and   etching into the semiconductor body to form recesses substantially aligned to the gate structure wherein dopant of the source/drain implant is substantially removed therefrom;   performing a selective epitaxial growth in the recesses.   
     
     
         9 . The method of  claim 8 , wherein performing the selective epitaxial growth further comprises a deposition of silicon germanium in the presence of a boron dopant containing source gas, wherein the boron dopant dopes the epitaxially grown silicon germanium in-situ. 
     
     
         10 . The method of  claim 8 , wherein performing the selective epitaxial growth comprises growing a boron doped silicon germanium in the recesses. 
     
     
         11 . The method of  claim 1 , further comprising forming sidewall spacers on the lateral edges of the gate structure before forming the recesses, wherein the recesses are aligned in the semiconductor body with respect to offset spacers. 
     
     
         12 . The method of  claim 8 , wherein the source/drain implant further comprises performing at least one angled implant, wherein the at least one angled implant results in doping contacting a top portion of the gate structure. 
     
     
         13 . The method of  claim 8 , wherein the first conductivity type is n-type and the second conductivity type is p-type. 
     
     
         14 . The method of  claim 8 , wherein the source/drain implant is a dose concentration in the range of about 1E15 to 4E15 ions/cm 2  and wherein etching into the semiconductor body to form recess removes all of the source/drain implant. 
     
     
         15 . The method of  claim 1 , further comprising:
 forming extension regions of a second conductivity type adjacent to the gate structure.