A method includes forming a metal gate structure, wherein the metal gate structure includes a gate dielectric layer and a gate electrode; performing a surface treatment to a top surface of the metal gate structure, wherein the surface treatment converts a top portion of the gate electrode to an oxidation layer; forming a conductive layer above the gate electrode, wherein the forming of the conductive layer includes substituting oxygen in the oxidation layer with a metallic element; and forming a contact feature above the metal gate structure, wherein the contact feature is in direct contact with the conductive layer.