A semiconductor device includes a semiconductor substrate, an interlayer dielectric layer on the semiconductor substrate, a plurality of trenches extending through the interlayer dielectric layer to the semiconductor substrate and comprising a first trench of a PMOS device and a second trench of an NMOS device, a high-k dielectric layer on a bottom and sidewalls of the trenches, a PMOS work function adjustment layer on the high-k dielectric layer in the first trench, an NMOS work function adjustment layer on the high-k dielectric layer in the second trench, and a metal electrode layer on the PMOS work function adjustment layer in the first trench and on the NMOS work function adjustment layer in the second trench.