One or more exemplary embodiments disclose a thin film transistor array panel and a manufacturing method thereof including a substrate, a gate line on the substrate, the gate line including a gate electrode, a gate insulating layer on the gate electrode, a semiconductor layer on the gate insulating layer, and the semiconductor layer including an oxide semiconductor, a data wire layer above the semiconductor layer, the data wire layer including a data line, a source electrode coupled to the data line, and a drain electrode facing the source electrode, and a metal phosphorus oxide layer configured to cover the source electrode and the drain electrode.