US Patent 7952118 Semiconductor device having different metal gate structures

A semiconductor includes a channel region in a semiconductor substrate, a gate dielectric film on the channel region, and a gate on the gate dielectric film. The gate includes a doped metal nitride film, formed from a nitride of a first metal and doped with a second metal which is different from the first metal, and a conductive polysilicon layer formed on the doped metal nitride film. The gate may further include a metal containing capping layer interposed between the doped metal nitride film and the conductive polysilicon layer.