Reducing the dielectric constant of a portion of a gate dielectric

Abstract

In a metal gate replacement process, a cup-shaped gate metal oxide dielectric may have a vertical portion that may be exposed to a silicon ion implantation. As a result of the implantation, the dielectric constant of a vertical portion may be reduced, reducing fringe capacitance.

1 . A semiconductor structure comprising: 
 a semiconductor substrate;    a metal oxide gate dielectric over said substrate including a ternary silicate and a metal oxide; and    a metal gate electrode over said gate dielectric.    
   
   
       2 . The structure of  claim 1  wherein said dielectric includes a horizontal metal oxide portion that is substantially transverse to said ternary silicate.  
   
   
       3 . The structure of  claim 1  wherein said metal oxide has a dielectric constant greater than 10.  
   
   
       4 . The structure of  claim 3  wherein said ternary silicate is along side said gate electrode.  
   
   
       5 . The structure of  claim 4  wherein said metal oxide is under said gate electrode.