| 摘要 |
PURPOSE:To provide an input/output protection circuit having a high capacity to static electricity or the like without causing deterioration of characteristics such as decrease in operation speed or the like during normal operation, by adapting the circuit such that an input/output protection diode is connected to an input/output section only when a high voltage is applied. CONSTITUTION:An N<-> type substrate 18 is provided with a P-type resistance region 11, P<-> type well region 17 and P<+> type diffusion layers 7 and 8. The P<+> type diffusion layers 7 and 8 are adjacent to each other so closely that they are separated only by a depletion layer 15. In the P<-> type well region 17, N<+> type diffusion layers 9 and 10 are formed such that they are adjacent to each other so closely that they are seperated only by a depletion layer 16. The P<+> type diffusion layer 7 together with the N<-> type substrate 18 constitutes a protection diode 4, the P<+> type diffusion layer 8 together with the N<-> type substrate 18 constitutes a protection diode 6, the N<+> type diffusion layer 9 together with the P<-> well region 17 constitutes a protection diode 3 and the N<+> diffusion layer 10 together with the P<-> well region 17 constitutes a protection diode 5. An input terminal 1 is connected to the resistance region 11 by means of a connection wire while the resistance region 11 is connected only to the P<+> diffusion layer 7 and the N<+> diffusion layer 9. |
