A method of manufacturing a thin film transistor array substrate includes forming a gate pattern on a substrate, forming a gate insulating film on the substrate, forming a source/drain pattern and a semiconductor pattern on the substrate, forming first, second, and third passivation films successively on the substrate. Over the above multi-layered passivation film forming a first photoresist pattern including a first portion formed on part of the drain electrode and on the pixel region, and a second portion. The second portion is thicker than the first portion. Then, patterning the third passivation film using the first photoresist pattern, forming a second photoresist pattern by removing the first portion of the first photoresist pattern, forming a transparent electrode film on the substrate, removing the second photoresist pattern and the transparent electrode film disposed on the second photoresist pattern, and forming a transparent electrode pattern on the second passivation layer.