Provided is a method of fabricating a semiconductor device. In one embodiment, the method includes forming at least one unit device in a substrate and on a front side of the substrate, forming a through-silicon via (TSV) structure apart from the at least one unit device to substantially vertically penetrate the substrate, the TSV structure having a back end including a concave portion, forming an internal circuit on the front side of the substrate and a front end of the TSV structure to be electrically connected to the at least one unit device and the front end of the TSV structure, forming a front side bump on the front side of the substrate to be electrically connected to the front end of the TSV structure, forming a redistribution layer on a back side of the substrate to be electrically connected to the back end of the TSV structure, and forming a back side bump to be electrically connected to the redistribution layer.