A thin film transistor array panel is provided and includes a gate line, a gate insulating layer covering the gate line, a semiconductor layer disposed on the gate insulating layer, and a data line and a drain electrode disposed on the semiconductor layer. The data line and the drain electrode have a dual-layered structure including a lower layer and an upper layer with the lower layer having a first portion protruded outside the upper layer and the semiconductor layer having a second portion protruded outside the edge of the lower layer.