A metal oxide semiconductor field effect transistor (MOSFET) includes a semiconductor substrate and an interlayer dielectric (ILD) over the semiconductor substrate. A gate structure is formed within the ILD and disposed on the semiconductor substrate, wherein the gate structure includes a high-k dielectric material layer and a metal gate stack. One or more portions of a protection layer are formed over the gate stack, and a contact etch stop layer is formed over the ILD and over the one or more portions of the protection layer. The metal gate stack includes aluminum and the protection layer includes aluminum oxide.