A thin film transistor array panel, including: a first insulating substrate; a gate line disposed on the first insulating substrate and including a gate electrode; a semiconductor layer disposed on the gate electrode; a data conductor layer disposed on the semiconductor layer, and including a data line crossing the gate line, a source electrode connected to the data line and exposing at least a part of the semiconductor layer, and a drain electrode facing the source electrode; a capping layer disposed on the data conductor layer, the semiconductor layer exposed between the source electrode and the drain electrode, and the entire surface of the first insulating substrate; and a first passivation layer disposed on the capping layer. The capping layer and the semiconductor layer include the same material.