Forming dual metal complementary metal oxide semiconductor integrated circuits

Abstract

Complementary metal oxide semiconductor metal gate transistors may be formed by depositing a metal layer in trenches formerly inhabited by patterned gate structures. The patterned gate structures may have been formed of polysilicon in one embodiment. The metal layer may have a workfunction most suitable for forming one type of transistor, but is used to form both the n and p-type transistors. The workfunction of the metal layer may be converted, for example, by ion implantation to make it more suitable for use in forming transistors of the opposite type.

1 . A semiconductor structure comprising:
 a transistor of a first type including a gate electrode;   a transistor of a second type including a gate electrode, said transistor of a second type including a gate dielectric, a first metal over said gate dielectric, and a second metal over said first metal, said first metal having an altered workfunction.   
   
   
       2 . The structure of  claim 1  wherein the workfunction of said first metal has been increased. 
   
   
       3 . The structure of  claim 2  wherein said transistor of a first type has a metal layer of the same material as the first metal layer of said transistor of a second type but said first metal layer has a different workfunction than said metal layer of said transistor of a first type. 
   
   
       4 . The structure of  claim 3  wherein said transistor of said first type is an n-type transistor and said transistor of a second type is a p-type transistor. 
   
   
       5 . The structure of  claim 4  wherein said transistors include a gate dielectric layer having a dielectric constant greater than 10.