A thin film transistor array panel is provided, which includes a substrate including a display region, a chip region, and a pad region; a plurality of signal lines formed on the substrate for electrically connecting the pad region to the chip region and the display region, wherein the signal lines have pads as an end portion and the pads are formed in the pad region; an insulating layer covering the signal lines and having a plurality of contact holes exposing the portions of the signal lines; a plurality of contact assistants formed on the insulating layer and connected to the pads through the contact holes; and a plurality of connection member respectively connected to the contact assistants and formed on the insulating layer for selectively electrically connecting the signal lines, wherein the insulating layer has a boundary line formed by etching, and the boundary line is crenellated.