A semiconductor device may include a substrate including a first surface and a second surface, which are opposite to each other, an insulating layer on the first surface of the substrate, a first via structure and a second via structure penetrating the substrate and a portion of the insulating layer and having different widths from each other in a direction parallel to the first surface of the substrate, metal lines provided in the insulating layer, and an integrated circuit provided on the first surface of the substrate. A bottom surface of the first via structure may be located at a level lower than a bottom surface of the second via structure, when measured from the first surface of the substrate. The second via structure may be electrically connected to the integrated circuit through the metal lines.