Semiconductor devices, and methods of fabricating a semiconductor device, include forming a via hole through a first surface of a substrate, the via hole being spaced apart from a second surface facing the first surface, forming a first conductive pattern in the via hole, forming an insulating pad layer on the first surface of the substrate, the insulating pad having an opening exposing the first conductive pattern, performing a thermal treatment on the first conductive pattern to form a protrusion protruding from a top surface of the first conductive pattern toward the opening, and then, forming a second conductive pattern in the opening.