A semiconductor device includes a substrate, an interlayer insulating layer on the substrate, a first etch stop layer on the substrate, a first through-silicon-via (TSV) configured to pass vertically through the substrate and the interlayer insulating layer, and a second TSV configured to pass vertically through the substrate, the interlayer insulating layer, and the first etch stop layer, wherein the second TSV has a width greater than that of the first TSV.