Replacement gates to enhance transistor strain

Abstract

Some embodiments of the present invention include apparatuses and methods relating to NMOS and PMOS transistor strain.

1 . A method comprising:
 forming an NMOS transistor including a channel, a stressor, and a gate structure over the channel and between sidewall spacers, wherein the stressor causes a tensile strain on the channel; and   removing at least a portion of the gate structure to allow the stressor to enhance the tensile strain on the channel, wherein removing the portion of the gate structure forms a trench.   
     
     
         2 . The method of  claim 1 , wherein the stressor comprises a tensile layer over the gate structure. 
     
     
         3 . The method of  claim 1 , wherein removing the portion of the gate structure includes removing a gate electrode, and wherein a gate dielectric remains. 
     
     
         4 . The method of  claim 3 , wherein the gate dielectric comprises a high-k gate dielectric. 
     
     
         5 . The method of  claim 4 , further comprising:
 forming a metal gate electrode over the high-k gate dielectric.   
     
     
         6 . A method comprising:
 forming a PMOS transistor including a channel, a stressor, and a gate structure over the channel and between sidewall spacers, wherein the stressor causes a compressive strain on the channel; and   removing at least a portion of the gate structure to allow the stressor to enhance the compressive strain on the channel, wherein removing the portion of the gate structure forms a trench.   
     
     
         7 . The method of  claim 6 , wherein the stressor comprises an epitaxial source and drain film. 
     
     
         8 . The method of  claim 6 , wherein removing the portion of the gate structure includes removing a gate electrode and a gate dielectric. 
     
     
         9 . The method of  claim 8 , further comprising:
 forming a high-k gate dielectric in the trench; and   forming a metal gate electrode over the high-k gate dielectric, wherein the metal gate electrode provides an additional compressive strain in the channel.