Semiconductor devices and methods for manufacturing the same are disclosed. In one embodiment, the method comprises: sequentially forming a sacrificial layer and a semiconductor layer on a substrate; forming a first cover layer on the semiconductor layer; forming an opening extending into the substrate with the first cover layer as a mask; selectively removing at least a portion of the sacrificial layer through the opening, and filling an insulating material in a gap due to removal of the sacrificial layer; forming one of source and drain regions in the opening; forming a second cover layer on the substrate; forming the other of the source and drain regions with the second cover layer as a mask; removing a portion of the second cover layer; and forming a gate dielectric layer, and forming a gate conductor in the form of spacer on a sidewall of a remaining portion of the second cover layer.