| 摘要 |
PURPOSE:To simplify structure, and to utilize an element surface effectively by providing a switching means through which one conduction type semiconductor region, potential thereof must be returned at an opportune time, and an element isolation region are brought to a conductive state at the opportune time. CONSTITUTION:When reading pulse voltage VR is applied for a fixed time and polysilicon 14 is brought to ground potential, a p-base region 9 is brought to a reverse bias state to an n<+> emitter region 15, the change of potential of the n<+> emitter region 15 stops, and informations on the emitter side are read to the outside through polysilicon 13 and an electrode 19. When reading is completed, the electrode 19 is grounded, and the n<+> emitter region 15 is brought to ground potential, but optical informations must be eliminated because the potential of the p-base region 9 corresponds to the intensity of light under the state. Accordingly, when negative pulse voltage VRH exceeding the threshold voltage Vth of a p-MOS transistor is applied to polysilicon 14 through an electrode 17, the p- MOS transistor is brought to a conductive state, holes stored in the p-base region 9 are removed, and the potential of the p-base region 9 is fixed at predetermined negative voltage applied to a p<+> element isolation region 6. |
