Aspects of the disclosure provide a method for fabricating a semiconductor device. A pre-stress liner is formed over a structure. The structure includes a gate structure having sidewalls. A protection layer is formed. The protection layer covers a first portion of the pre-stress liner that extends along the sidewalls of the gate structure, and exposes a second portion of the pre-stress liner that is away from the sidewalls of the gate structure. An oxygen-containing layer is formed. The oxygen-containing layer covers the pre-stress liner and the protection layer. The oxygen-containing layer is separated from the first portion of the pre-stress liner by the protection layer. The structure is annealed such that the second portion of the pre-stress liner oxidizes by receiving oxygen from the oxygen-containing layer, while the first portion of the pre-stress liner remains unoxidized due to the protection layer.