An integrated circuit is provided including an FET gate structure formed on a substrate. This structure includes a gate dielectric on the substrate, and a metal nitride layer overlying the gate dielectric and in contact therewith. This metal nitride layer is characterized as MNx, where M is one of W, Re, Zr, and Hf, and x is in the range of about 0.7 to about 1.5. Preferably the layer is of WNx, and x is about 0.9. Varying the nitrogen concentration in the nitride layer permits integration of different FET characteristics on the same chip. In particular, varying x in the WNx layer permits adjustment of the threshold voltage in the different FETs. The polysilicon depletion effect is substantially reduced, and the gate structure can be made thermally stable up to about 1000° C.