Display devices, display modules, and methods of manufacture are disclosed. In one example, a display device includes a pixel region in which pixels for displaying an image are arranged, on an upper surface of a substrate. A device-side signal electrode for exchanging a signal related to the pixels with an outside is disposed on a side surface of the substrate. A module casing is configured to store the display device and to have a casing-side signal electrode electrically connected to the device-side signal electrode in a spot facing the device-side signal electrode.