Semiconductor memory device clamping the overshoot and undershoot of input signal by circuit with PN junction

摘要

An input signal applied to a terminal receiving an external signal (e.g. a data input/output terminal DQj) is transmitted by an input signal line. A p well formed in a main surface of a p substrate is electrically isolated from the p substrate by an n well and a triple n well. The p well and the n well receive a potential level of the signal input line. An n diffusion layer is formed in a main surface of the p well and receives an external power supply potential Vdd.