The present disclosure describes a semiconductor device. The device includes a semiconductor substrate, an isolation structure formed in the substrate for isolating a first active region and a second active region, a first transistor formed in the first active region, the first transistor having a high-k gate dielectric layer and a metal gate with a first work function formed over the high-k gate dielectric layer, and a second transistor formed in the second active region, the second transistor having the high-k gate dielectric layer and a metal gate with a second work function formed over the high-k gate dielectric layer. The metal gates are formed from at least a single metal layer having the first work function and the second work function.