Patent ID: 8658489

Claim:
A method of forming a device, comprising the steps of: providing a semiconductor body having a NMOS gate stack, a PMOS gate stack, and an oxide layer formed thereon, wherein the NMOS gate stack comprises a first gate dielectric, a first mid-gap metal gate, and a first dummy poly layer and the PMOS gate stack comprises a second gate dielectric, a second mid-gap metal gate, and a second dummy poly layer; removing the first dummy poly layer and the second dummy poly layer; performing a low temperature oxidation to incorporate oxygen into the first mid-gate metal gate and the second mid-gap metal gate; depositing a first cap layer over the NMOS gate stack and the PMOS gate stack; removing the first cap layer from one of the NMOS gate stack and PMOS gate stack; depositing a second cap layer over both the NMOS gate stack and the PMOS gate stack, wherein one of the first cap layer and the second cap layer comprise a low oxygen affinity and high work function material and the other comprises a high oxygen affinity and low work function material such that oxygen is scavenged from the first mid-gap metal gate; and after depositing the second cap layer, annealing the device to incorporate low work function material into the first mid-gap metal gate at an interface between the first mid-gap metal gate and the first gate dielectric.