A metal gate transistor includes a substrate, a metal gate on the substrate, and a source/drain region in the substrate adjacent to the metal gate. The metal gate includes a high-k dielectric layer, a bottom barrier metal (BBM) layer comprising TiSiN on the high-k dielectric layer, a TiN layer on the BBM layer, a TiAl layer between the BBM layer and the TiN layer, and a low resistance metal layer on the TiN layer.