A semiconductor device and a fabrication method are provided. The fabrication method includes providing a gate structure on a substrate and a first protective layers on the gate structure; forming an initial sidewall spacer on a sidewall of each of the gate structure and the first protective layer; forming a first sidewall spacer on a sidewall of the initial sidewall spacer, the first and initial sidewall spacers being made of different materials; forming a second sidewall spacer by removing a portion of the initial sidewall spacer, leaving a trench formed above the second sidewall spacer and between the first sidewall spacer and the first protective layer; and forming a second protective layer in the trench, the second protective layer and the first sidewall spacer being made of a same material. The second sidewall spacer has a top surface higher than or level with a top surface of the gate structure.