A metal gate transistor is disclosed. The metal gate transistor includes a substrate, a metal gate on the substrate, and a source/drain region in the substrate. The metal gate further includes a high-k dielectric layer, a bottom barrier metal (BBM) layer on the high-k dielectric layer, a first work function layer on the BBM layer, a second work function layer between the BBM layer and the first work function layer, and a low resistance metal layer on the first work function layer. Preferably, the first work function layer includes a p-type work function layer and the second work function layer includes a n-type work function layer.