A method includes forming a trench over a substrate, wherein the trench is surrounded by gate spacers and an inter-layer dielectric layer, depositing a dielectric layer on a bottom and along sidewalls of the trench, depositing a metal layer over the dielectric layer, depositing a protection layer over the metal layer, wherein the protection layer has an uneven thickness, applying an etch-back process to the protection layer and the metal layer, wherein as a result of applying the etch-back process, a portion of the metal layer has been removed and at least a portion of the protection layer remains at the bottom of the trench and removing the protection layer from the trench.