Display device, method of manufacturing the same, and tiled display device having the same

A method of manufacturing a display device, the method comprising:

• forming a display element layer and a pixel circuit layer on a first surface of a substrate, the display element layer comprising a light emitting element;
• forming an opening passing through the substrate with the display element layer formed thereon from a second surface facing the first surface to the first surface of the substrate to expose at least a portion of the pixel circuit layer;
• filling the opening from the second surface of the substrate and forming a connection portion contacting the exposed portion of the pixel circuit layer;
• and
• forming a capping layer having a pad opening exposing a portion of the connection portion on the second surface of the substrate,
• wherein the opening is formed in a display area of the substrate at where an image is displayed,
• wherein the capping layer covers another portion of the connection portion on the second surface of the substrate,
• wherein the forming of the pixel circuit layer comprises:
• forming a semiconductor layer on the first surface of the substrate;
• forming a gate electrode on the semiconductor layer;
• forming a signal line disposed on a same layer as the gate electrode;
• and
• forming a first transistor electrode and a second transistor electrode disposed on the gate electrode and electrically connected to the semiconductor layer,
• wherein the forming of the opening comprises exposing the signal line,
• wherein the forming of the connection portion comprises forming a through electrode filling the opening and a fan-out electrode covering the second surface of the substrate, and
• wherein the through electrode extends continuously in a thickness direction of the substrate between the signal line and the fan-out electrode, and comprises a through end portion contacting a flat bottom surface of the signal line.