The present disclosure provides a semiconductor device and a fabrication method. The method includes: providing a substrate; forming at least one sacrificial layer and at least one liner layer, that are alternately stacked over each other, on the substrate; etching the at least one liner layer and the at least one sacrificial layer until the substrate is exposed, to form a plurality of fins, discretely arranged on the substrate; and etching a portion of a thickness of the substrate, such that a width of the etched portion of the substrate at a bottom of the at least one sacrificial layer is less than a width of the at least one liner layer of the plurality of fins.