A thin film transistor array panel according to an exemplary embodiment of the present invention comprises a substrate, a gate line formed on the substrate, a gate insulating layer formed on the gate line, a semiconductor layer formed on the gate insulating layer, and a data line formed on the semiconductor layer, wherein the data line comprises a lower data layer, an upper data layer, a data oxide layer, and a buffer layer, wherein the upper data layer and the buffer layer comprise a same material.