A method for fabricating a strained channel semiconductor structure includes providing a substrate, forming at least one gate structure on said substrate, performing an etching process to form two recesses in said substrate at opposites sides of said gate structure, the sidewall of said recess being concaved in the direction to said gate structure and forming an included angle with respect to horizontal plane, and performing a pre-bake process to modify the recess such that said included angle between the sidewall of said recess and the horizontal plane is increased.