Dual metal gates for mugfet device

A method of forming a transistor device, comprising:

• forming a gate dielectric over NMOS and PMOS regions separated by an isolation region of a semiconductor substrate;
• forming an Al-containing metal layer over the gate dielectric over the NMOS and PMOS regions;
• patterning and etching the Al-containing metal layer to remove the Al-containing metal layer from over the gate dielectric layer over the NMOS region, while leaving the Al-containing metal layer over the gate dielectric layer over the PMOS region;
• after patterning and etching the Al-containing metal layer, forming a TiN or TaN metal layer over the gate dielectric layer over the NMOS region and over the Al-containing metal layer over the gate dielectric layer over the PMOS region;
• after forming the TiN or TaN metal layer, performing a thermal anneal to chemically combine the Al in the Al-containing metal layer and the TiN or TaN in the TiN or TaN metal layer to form a TiAlN or TaAlN PMOS gate material over the PMOS region;
• with the TiN or TaN left as an NMOS gate material over the NMOS region.