Patent ID: 8629014

Claim:
A method of forming a semiconductor structure comprising a first field effect transistor and a second field effect transistor, said method comprising: recessing disposable gate structures below a planar dielectric surface to form gate cavities over a semiconductor substrate; forming a stack that includes, from bottom to top, a SiO 2 layer on the semiconductor substrate, a contiguous gate dielectric layer that is in direct contact with a single first-type work function metal layer comprising a first metal having a first work function, and a single barrier metal layer in said gate cavities and on said planar dielectric surface, wherein the single barrier metal layer is in direct contact with the single first-type work function metal layer that separates the single barrier metal layer from the contiguous gate dielectric layer; patterning said single barrier metal layer and said single first-type work function metal layer, wherein said single barrier metal layer and said single first-type work function metal layer are present in a first gate cavity, and said single barrier metal layer and said single first-type work function metal layer are removed in a second gate cavity during said patterning; and forming a second-type work function metal layer comprising a second metal having a second work function on said single barrier metal layer in said first gate cavity and a portion of said contiguous gate dielectric layer in said second gate cavity, wherein one of said first and second work functions is closer to a conduction band of a semiconductor material of the semiconductor substrate than a valence band of the semiconductor material, of said semiconductor substrate and the other of said first and second work functions is closer to said valence band than to said conduction band, wherein the one of said first and second work functions that is closer to the conduction band is provided by a metal selected from the group consisting of Hf, Ti, Zr, Cd, La, Tl, Yb, Al, Ce, Eu, Li, Pb, Tb, Bi, In, Lu, Nb, Sm, V, Zr, Ga, Mg, Gd, Y, TiAl and alloys thereof, and the other of said first and second work functions that is closer to said valence band is provided by a metal that is selected from the group consisting of Pt, Rh, Ir, Ru, Cu, Os, Be, Co, Pd, Te, Cr, Ni, TiN and alloys thereof.