Display device and tiled display device including the same

A display device comprising:

• a substrate comprising a first contact hole;
• a thin-film transistor layer on a first surface of the substrate and comprising a plurality of insulating layers and a thin-film transistor;
• an etching stopper on one or more of the insulating layers and contacting the substrate through a second contact hole surrounding the first contact hole in a plan view;
• a connection line on the etching stopper;
• and
• a pad part on a second surface of the substrate opposite the first surface of the substrate and connected to the connection line through the first contact hole,
• wherein the first contact hole and the second contact hole are spaced apart from each other in a common layer in a plan view.