Various embodiments provide metal gate transistors and methods for forming the same. In an exemplary method, a substrate having a top surface and a back surface can be provided. A dummy gate can be formed on the top surface. A first interlayer dielectric layer can be formed on the top surface and planarized to expose the dummy gate. The dummy gate can be removed to form a trench. A metal gate stack can be formed to cover the first interlayer dielectric layer and to fill the trench. The metal gate stack can be planarized to remove a portion of the metal gate stack from the first interlayer dielectric layer to form a metal gate electrode in the trench. A remaining edge portion of the metal gate stack can exist over an annular region of the substrate and can be removed from the annular region by an edge cleaning process.