A method for fabricating a semiconductor device includes forming a gate electrode structure over a first region of a semiconductor substrate, and selectively forming an oxide layer overlying the gate electrode structure by reacting a halide compound with oxygen to increase a height of the gate electrode structure. The halide compound may be silicon tetrachloride, and the oxide layer may be silicon dioxide. The gate electrode structure may be a dummy gate electrode, which is subsequently removed, and replaced with another gate electrode structure.