A radiation image sensor comprising: a charge generation section absorbing radiation to generate charge; and a circuit board accumulating and transferring the charge generated in the charge generation section , wherein the charge generation section is disposed on the circuit board , wherein the circuit board includes: a semiconductor substrate ; a capacitive section accumulating the charge generated in the charge generation section ; and a MOS transistor in the semiconductor substrate, the MOS transistor including one end connected to the capacitive section and another end connected to a wire transferring the charge, wherein each of the one end and the another end are impurity diffused regions, and wherein the capacitive section includes a partial region of the semiconductor substrate , a conductor layer disposed on the partial region and electrically connected to the charge generation section , and an insulating layer interposed between the partial region and the conductor layer , characterised in that an upper surface of the conductor layer is electrically connected with the one end of the MOS transistor through intra-layer and inter-layer wiring disposed on the semiconductor substrate , wherein the capacitive section further includes an additional impurity diffused region in which an impurity to impart a conductivity type different from a conductivity type of the semiconductor substrate is diffused, the additional impurity diffused region being located next to the partial region of the semiconductor substrate , wherein the additional impurity diffused region and the conductor layer are electrically connected to each other. a charge generation section absorbing radiation to generate charge; and a circuit board accumulating and transferring the charge generated in the charge generation section , wherein the charge generation section is disposed on the circuit board , wherein the circuit board includes: a semiconductor substrate ; a capacitive section accumulating the charge generated in the charge generation section ; and a MOS transistor in the semiconductor substrate, the MOS transistor including one end connected to the capacitive section and another end connected to a wire transferring the charge, wherein each of the one end and the another end are impurity diffused regions, and a semiconductor substrate ; a capacitive section accumulating the charge generated in the charge generation section ; and a MOS transistor in the semiconductor substrate, the MOS transistor including one end connected to the capacitive section and another end connected to a wire transferring the charge, wherein each of the one end and the another end are impurity diffused regions, and wherein the capacitive section includes a partial region of the semiconductor substrate , a conductor layer disposed on the partial region and electrically connected to the charge generation section , and an insulating layer interposed between the partial region and the conductor layer , characterised in that an upper surface of the conductor layer is electrically connected with the one end of the MOS transistor through intra-layer and inter-layer wiring disposed on the semiconductor substrate , wherein the capacitive section further includes an additional impurity diffused region in which an impurity to impart a conductivity type different from a conductivity type of the semiconductor substrate is diffused, the additional impurity diffused region being located next to the partial region of the semiconductor substrate , wherein the additional impurity diffused region and the conductor layer are electrically connected to each other. <EOS>