| 摘要 |
Independently of a punch-through MOS transistor Q3 used as an I/O protection element in which the drain is connected to an input node or output node and the source is connected to a GND or Vcc, an element for-setting the gate of punch-through MOS transistor Q3 to the GND potential is provided so that its operating speed may be slower than the punch-through speed of the punch-through MOS transistor Q3. In consequence, a high surge applied from I/O terminal can be punched through before the gate insulating film of the punch-through transistor Q3 undergoes a high electric field, to thereby protect the gate insulating film.
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