A semiconductor device and a method for manufacturing the same. An example method may include: forming a first semiconductor layer and a second semiconductor layer sequentially on a substrate; patterning the second and first semiconductor layers to form an initial fin; forming an isolation layer on the substrate, wherein the isolation layer exposes partially the first semiconductor layer, and thus defines a fin above the isolation layer; and forming a gate stack intersecting the fin on the isolation layer, wherein the first semiconductor layer comprises a compound semiconductor, with at least one component whose concentration has a graded distribution in a stack direction of the first and second semiconductor layers.