A method of manufacturing a thin film transistor substrate includes forming a semiconductor pattern on a substrate, wherein the semiconductor pattern includes a first area, a second area, and a third area, wherein the second area and the third area are located on each side of the first area; forming an insulating layer on the substrate to cover the semiconductor pattern; forming a metal pattern layer on the insulating layer using a first photosensitive pattern; doping the semiconductor pattern with first impurities using the first photosensitive pattern; forming a gate electrode by patterning the metal pattern layer using a second photosensitive pattern; and doping the semiconductor pattern with second impurities having a lower concentration than the first impurities.