A method of manufacturing a thin film transistor array panel including forming a gate line on a substrate, forming a gate insulating layer on the gate line, forming a semiconductor layer on the gate insulating layer, forming a data line and a drain electrode on the semiconductor layer, depositing a passivation layer on the data line and the drain electrode, forming a photoresist including a first portion and a second portion, which is thinner than the first portion, on the passivation layer, etching the passivation layer using the photoresist as a mask to expose a portion of the drain electrode, removing the second portion of the photoresist, depositing a conductive film, and removing the first portion of the photoresist to form a pixel electrode on the exposed portion of the drain electrode.