APPARATUS FOR PREVENTING ELECTROSTATIC BREAKDOWN OF SEMICONDUCTOR DEVICE

摘要

PURPOSE:To absorb both positive and negative surge pulses by forming an n<+> type buried layer as a protection resistance and using a junction diode composed of the n<-> type region and the p type diffused region. CONSTITUTION:When a forward surge pulse enters the electrode in the input terminal side, a voltage drops due to a resistance while a surge current flows into the n<+> type buried layer 5. Thereby, an input voltage is clamped to a value which is equal to a breakdown voltage of the p-n junction diode D1 between the n<-> type region 6a and p type region 9. Namely, holes are implanted to a low potential p type layer 9 from the n<-> type region 6a, causing a current I1 to flow and absorbing a surge pulse. A backward surge current operates the p-n junction diode between the n<-> type region 6a and the p type diffused layer 9 and an input voltage is clamped to a voltage (GND-VF) which is equal to a difference between the ground voltage and forward voltage VF of diode, causing electrons to be implanted to the side of p type diffused layer 9 from the n<-> type region 6a.