A substrate includes a thin film transistor (TFT) which includes an active layer, a gate electrode, a source electrode, and a drain electrode; a first insulating layer disposed between the active layer and the gate electrode; a second insulating layer disposed between the gate electrode and the source and drain electrodes; a third insulating layer disposed on the second insulating layer, and including a first region for opening the second insulating layer and a second region for opening one of the source and drain electrodes, the first region and the second region being integrally connected; and a first electrode connected to one of the source and drain electrodes, and disposed so as to cover the first region and the second region.