A method of manufacturing a thin film transistor array panel includes forming an amorphous silicon film on an insulating substrate; forming a sacrificial film having an embossed surface on the amorphous silicon film; contacting a metal plate with the sacrificial film and performing heat-treatment for crystallizing the amorphous silicon film to change the amorphous silicon film to a polycrystalline silicon film; removing the metal plate and the sacrificial film; patterning the polycrystalline silicon film to form a semiconductor; forming a gate insulating layer which covers the semiconductor; forming a gate line on the gate insulating layer, a portion of the gate line overlapping the semiconductor; heavily doping a conductive impurity into portions of the semiconductor to form a source region and a drain region; forming an interlayer insulating layer which covers the gate line and the semiconductor; and forming a data line and an output electrode connected to the source and drain regions, respectively, on the interlayer insulating layer.