Integration scheme for multiple metal gate work function structures

摘要

A metal gate stack containing a metal layer having a mid-band-gap work function is formed on a high-k gate dielectric layer. A threshold voltage adjustment oxide layer is formed over a portion of the high-k gate dielectric layer to provide devices having a work function near a first band gap edge, while another portion of the high-k dielectric layer remains free of the threshold voltage adjustment oxide layer. A gate stack containing a semiconductor oxide based gate dielectric and a doped polycrystalline semiconductor material may also be formed to provide a gate stack having a yet another work function located near a second band gap edge which is the opposite of the first band gap edge. A dense circuit containing transistors of p-type and n-type with the mid-band-gap work function are formed in the region containing the threshold voltage adjustment oxide layer.