The present invention discloses a method to manufacture metal gate of integrated circuits. A gate oxide layer is formed on a substrate and a polysilicon layer is then deposited on the gate oxide layer. Afterwards, a barrier layer is formed on the polysilicon layer and a metal layer is deposited on the barrier layer. An etching process is performed to etch the metal layer and the barrier layer, and a metal gate is defined. Then, silicon nitride liners are formed on the sidewalls of the metal gate. Finally, silicon nitride spacers are formed on the silicon nitride liners and on the sidewalls of the polysilicon gate to serve as an insulating layer.