A thin-film transistor substrate includes a gate line, a capacitor dielectric layer, a gate insulation layer, an active pattern, a data line, a protection layer, and a pixel electrode. The gate wiring including a gate electrode, a lower storage electrode, and a gate metal pad is disposed on a substrate. The capacitor dielectric layer is disposed on the lower storage electrode and the gate insulation layer is disposed on the substrate. The active pattern includes an active layer and a dummy active layer disposed on the gate insulation layer in a gate electrode region and a gate metal pad region, respectively. A portion of the upper storage electrode is disposed on the capacitor dielectric layer exposed through a first contact hole in the gate insulation layer.