| 摘要 |
PURPOSE:To increase the strength against damage to external abnormal voltages, by connecting the transistor having high threshold voltage and diffusion resistance formed on the same semiconductor substrate to the transistor to be protected. CONSTITUTION:To the input transistor T1 to be protected, the resistor R1 having accompanied diode D1 and capacitor C1 is connected. Further, the resistor R2 having accompanied D2 and C2 and the resistor R3 accompanied with D3 and C3 are connected in series, and between the junction of the resistors R1 and R2 and the junction of R2 and R3, transistor Ts having greater capacitance Cs between the substrate and the junctions is provided. The transistor Ts plays sufficient protective functions, the gate oxide film is made thick and the threshold voltage is remarkably made greater than that of the transistor T1. Thus, transistors T1 and T3 are provided on one semiconductor substrate, forming greater capacitance Cs to the source diffusion layer 12 of Ts, and the resistors R1 to R3 are constituted with the diffusion resistance layers 5 to 7. |
