A thin film transistor array panel may include a channel layer including an oxide semiconductor and formed in a semiconductor layer, a source electrode formed in the semiconductor layer and connected to the channel layer at a first side, a drain electrode formed in the semiconductor layer and connected to the channel layer at an opposing second side, a pixel electrode formed in the semiconductor layer in a same portion of the semiconductor layer as the drain electrode, an insulating layer disposed on the channel layer, a gate line including a gate electrode disposed on the insulating layer, a passivation layer disposed on the source and drain electrodes, the pixel electrode, and the gate line, and a data line disposed on the passivation layer. A width of the channel layer may be substantially equal to a width of the pixel electrode in a direction parallel to the gate line.