A method of semiconductor device fabrication includes forming a first dummy gate structure in a first region of a semiconductor substrate and forming a second dummy gate structure in a second region of the semiconductor substrate. A protective layer (e.g., oxide and/or silicon nitride hard mask) is formed on the second dummy gate structure. The first dummy gate structure is removed after forming the protective layer, thereby providing a first trench. A capping layer (e.g., silicon) is formed in the first trench. A metal gate structure may be formed on the capping layer. The protective layer may protect the second dummy gate structure during the removal of the first dummy gate structure.