Abstract: An X-ray image sensor having a photoelectric conversion part that converts X-ray photons into electric charges. The X-ray image sensor includes a pixel electrode for collecting the electric charges and a storage capacitor for storing the electric charges collected by the pixel electrode. The storage capacitor includes a first capacitor electrode, the pixel electrode, and a dielectric layer that is deposited on the first capacitor electrode. The pixel electrode contacts an electron transport electrode via a hole through the dielectric layer. A switching TFT controls the release of electric charges in the storage capacitor to an external circuit. The switching TFT is comprised of a gate electrode, a first insulation film, a drain electrode, and a source electrode that contacts the electron transport electrode.