Semiconductor device for integrated injection logic

A semiconductor device for integrated injection logic comprising a semiconductor substrate of a first conductivity type, a signal input region of a second conductivity type provided in said semiconductor layer of said first conductivity type, at least one signal output region of said first conductivity type formed in said signal input region, a charge injection region of said second conductivity type of high impurity concentration provided closely to said signal input region and forming a pn junction with said semiconductor substrate of said first conductivity type, and electrodes provided for said substrate, signal input region, signal output regions and charge injection region, respectively, wheretby an inverted signal of an input signal is obtained by applying a forward bias voltage to said pn junction, said signal input region including a first portion of said second conductivity type having a lower impurity concentration than said charge injection region and a second portion having the same conductivity type as said first portion and having a higher impurity concentration than said first portion, said second portion being adjoined directly to said signal output region and connected to said signal input electrode, and said first portion being adjoined directly to at least the entire under surface of said portion.