| 摘要 |
PURPOSE:To apply an input surge voltage to a ground by uniformly distributing it by varying a threshold voltage by altering a polysilicon resistor and the thickness of a gate insulating film in combination with a protecting MIS transistor for varying the threshold voltage. CONSTITUTION:An input protecting circuit has an input pad formed of aluminum, a polysilicon resistor 2 made of an N<+> type polysilicon layer formed on the field insulating film of a semiconductor substrate 3, and a protecting MIS transistor 4. The transistor 4 is formed by separating source and drain regions 5, 6 made of N<+> type diffused layers, the thickness of a gate insulating film 8 on a channel region 7 is varied. An input surge voltage is uniformly dispersed in the transistor according to the amplitude of the threshold voltage. |
