| 摘要 |
PURPOSE:To improve the withstand voltage of the input protection circuit by a method wherein an impurity region of reverse conductivity type to that of the semiconductor substrate is formed in the substrate under a resistance wiring layer in the titled device having the resistance wiring layer for input protection circuit. CONSTITUTION:The input protection circuit consisting of a poly Si resistance wiring 14 and an aluminum field transistor 2 is formed between an input pin 50 and a wiring 51 led to the internal circuit. At this time, an N-well layer 21 is provided in the P type semiconductor substrate 11 at the part opposed to the resistance wiring layer 14. It follows that the resistance wiring layer 14, N-well layer 21, substrate 11, an N<+> layer 13', and an earth electrode 52 are connected with a series circuit of electrostatic capacitors C1, C2, and C3. Then, C2 reduces when the input pin 51 is plus, and C3 reduces when minus; therefore, a large voltage is not impressed on C1. Accordingly, since a large voltage is not impressed on an SiO2 film under the resistance layer 14, the input protection circuit can be increased in withstand voltage without break down. |
