A method of manufacturing a thin film transistor array substrate includes: forming a gate pattern on a substrate; forming a first gate insulating film and a second gate insulating film on the substrate; forming a source/drain pattern and a semiconductor pattern on the substrate; forming a passivation film on the substrate; forming a photo-resist pattern on the passivation film; patterning the passivation film using the photo-resist pattern to form a passivation film pattern, the patterning of the passivation film including over-etching the passivation film to form an open region in the passivation film; forming a transparent electrode film on the substrate; removing the photo-resist pattern and a portion of the transparent electrode film on the photo-resist pattern; and forming a pixel electrode on the first gate insulating layer.