| 摘要 |
PROBLEM TO BE SOLVED: To protect a cell data by providing a first well region connect with a ground voltage on a semiconductor substrate, providing a second well region in the first well region, and then forming a first impurity region connected with an I/O pad and a second impurity region connected with the ground voltage in that region. SOLUTION: Impurity regions 306-308 are applied with an identical voltage. More specifically, the impurity regions 306-308 are connected with a ground voltage VSS in a structure where an n-well 303 is used in a grounded p-type substrate 301 and connected with a power supply voltage VCC in a structure where a p-well 303 is used in an n-type substrate 301. When undershoot takes place in a signal flowing in through an I/O pad 101 and the diode connection between an n<+> region 305 and a p well region 304 is biased forward, multiple electrons are injected into the p well 304. When the ground voltage VSS is applied to the n-well 303, the majority of injected electrons are passed directly to the ground from the p well 304. |
