A thin-film transistor substrate is disclosed, which comprises a base layer; a semiconductor layer disposed on the base layer; a source electrode and a drain electrode disposed on the semiconductor layer; and a gate electrode disposed on the base layer and corresponding to the semiconductor layer; wherein the semiconductor layer includes a first region, a second region, and a third region, in which the first region corresponds to the gate electrode layer, the second region corresponds to the source electrode, and the third region corresponds to the drain electrode; and wherein the first region has a first thickness, the second region has a second thickness, and the third region has a third thickness, and the first thickness is greater than the second thickness or the third thickness.