| 摘要 |
PURPOSE:To obtain a semiconductor device capable of stably protecting input and output against overvoltage such as external surge by forming a P-N junction made of high density impurity region supplied with input and output signals in a high dielectric structure. CONSTITUTION:When an input signal IN is supplied to a metallic film 18, the signal is supplied through a hole 34 to a polysilicon film 33-1, then to an N<+> type layer 14-2, and when an external surge such as overvoltage is supplied to the metallic film, most of the surge current produced at that time is flowed through P-N junctions 35-1, 35-2 to ground side of a power line connected to P<+> type layers 12-1, 12-2. At this time, P type impurity regions 31-1, 31-2 forming the P-N junction are low density, and since the polysilicon film is connected to the metallic film, the film becomes equal potential to the N<+> type layer. Accordingly, the P-N junction and the thin insulating films 32-1, 32-2 are formed in high withstand voltage structure. Consequently, the damage of the junction of the P-N junction produced due to the supply of the concentrated surge current can be prevented. |
