US Patent 7332433 Methods of modulating the work functions of film layers

Methods for fabricating two metal gate stacks with varying work functions for complementary metal oxide semiconductor (CMOS) devices are provided A first metal layer may be deposited onto a gate dielectric, followed by the deposition of a second metal layer, where the second metal layer modulated the work function of the first metal layer. The second metal layer and subsequently etch, exposing a portion of the first metal layer. A third metal layer may be deposited on the etched second metal layer and the exposed first metal layer, where the third metal layer may modulate the work function of the exposed first metal layer. Subsequent fabrication techniques may be used to define the gate stack.