| 摘要 |
PURPOSE:To realize the extremely stable protection from an electrostatic breakdown even when a ground potential fluctuates due to the wiring resistance by a method wherein electrostatic-breakdown protective devices are installed at more than one position, i.e., at a position near an external-signal input terminal and at another position which is situated near an internal circuit of a semiconductor device and near a part where the ground wiring resistance is negligible. CONSTITUTION:MOS-type transistors are connected near a ground line for a semiconductor internal circuit 4. If a surge voltage is applied to an external-signal input terminal 1, a drain part 32 of a MOS transistor 3 near the external-signal input terminal fluctuates due to an equivalent ground wiring resistor 5. Even when a high voltage is applied to the internal circuit 4 without being suppressed sufficiently by the MOS- type transistor 3, a voltage at a drain part 42 of a MOS transistor 6 is suppressed by said MOS-type transistor by the internal circuit 4 is protected from a surge breakdown. In addition, even when a source part 41 of the MOS-type transistor 6 is easy to fluctuate, the ground line for the MOS-type transistor 6 fluctuates in the same manner as the ground line for the internal circuit 4; as a result, the internal circuit 4 is protected from a surge voltage. |
