A semiconductor device and a method for forming the semiconductor device are provided. The method includes providing a substrate, sequentially forming at least two sacrificial layers on the substrate, and forming a liner layer between any adjacent sacrificial layers of the at least two sacrificial layers. The method also includes forming a hard mask layer on a top layer of the at least two sacrificial layers, and sequentially etching the hard mask layer, the at least two sacrificial layers, the liner layer, and a portion of the substrate, thereby forming a plurality of fins that are discretely arranged on a remaining portion of the substrate. The method also includes forming a dummy gate structure across the plurality of fins on the remaining portion of the substrate, and removing a portion of the at least two sacrificial layers under the dummy gate structure, thereby forming tunnels.