A thin-film transistor (TFT) substrate is provided which includes: a substrate; a TFT disposed above the substrate; and a capacitor disposed above the substrate and electrically connected with the TFT, wherein the capacitor includes: a lower electrode layer disposed above the substrate and including an electrically conductive material as a main component; an upper electrode layer disposed above and opposed to the lower electrode layer and including, as a main component, an oxide semiconductor material to which electrical conductivity is given; and a capacitor insulating layer disposed between the lower electrode layer and the upper electrode layer. An extension extending outward from at least a portion of the outer edge of the lower electrode layer in plan view is provided to the lower electrode layer. In plan view, the upper electrode layer covers the lower electrode layer except the extension.