A dummy gate electrode and a dummy gate dielectric are removed to form a recess between adjacent gate spacers. A gate dielectric is deposited in the recess, and a barrier layer is deposited over the gate dielectric. A first work function layer is deposited over the barrier layer. A first anti-reaction layer is formed over the first work function layer, the first anti-reaction layer reducing oxidation of the first work function layer. A fill material is deposited over the first anti-reaction layer.