A semiconductor device is disclosed. The semiconductor device includes: a substrate; a gate structure disposed on the substrate; a first spacer disposed on a sidewall of the gate structure; a second spacer disposed around the first spacer, wherein the second spacer comprises a L-shaped cap layer and a cap layer on the L-shaped cap layer; a source/drain disposed in the substrate adjacent to two sides of the second spacer; and a CESL disposed on the substrate to cover the gate structure, wherein at least part of the second spacer and the CESL comprise same chemical composition and/or physical property.