| 摘要 |
PURPOSE:To increase the threshold voltage of other internal circuits while the threshold voltage of a transistor is left as it is dropped by previously preventing ion inplantation to a field oxide film on a transistor region when an input pin, a protective resistor and an internal circuit are connected in series and the transistor grounded between the resistor and the circuit is formed and used as an IC incorporating a protective circuit. CONSTITUTION:An input pin 11, a protective resistor R and an internal circuit 12 are connected in series, the gate and source of drain of a field transistor Tr for protection are connected to the connecting wire of the resistor R and the circuit 12, and the drain or the source is grounded. Ions are inplanted in a field insulating film in order to increase the threshold voltage of the parasitic field transistor of the internal circuit, but a region 15 surrounded by a one dot chain line in the Tr is coated with a mask at that time, and ion inplantation to the region is previously prevented. Figures 13, 14 shown in the figure are contact holes for connection. Accordingly, the increase of the potential of a node A is obviated even when surge is applied to the pin 11. |
