Semiconductor integrated circuit device including a dielectric breakdown

Abstract

A semiconductor integrated circuit device includes a dielectric breakdown prevention circuit coupled to an external terminal for protecting an input stage circuit. The prevention circuit has bipolar transistors and complementary MISFETs including a first MISFET of a first conductivity type and a second MISFET of a second conductivity type. A first semiconductor region of the first conductivity type is formed by the same layer as a well region in which the second MISFET is formed. A second semiconductor region of the second conductivity type is formed in said first semiconductor region by the same layer as source and drain regions of the second MISFET. These first and second semiconductor regions form a first PN junction diode. The external terminal is electrically coupled to one end portion of said second semiconductor region. A high impurity conductivity type buried third semiconductor region underlies the said second semiconductor region, and is formed by the same layer as a region isolating the bipolar transistors. This third region is disposed at the bottom surface of said first semiconductor region. A fourth semiconductor region of the second conductivity type is also formed in said first semiconductor region by the same layer used for collector contact regions of the bipolar transistors, and is connected with another end portion of said second semiconductor region, in contact with the third semiconductor region. The fourth semiconductor region is coupled to the input stage circuit, and the third and fourth semiconductor regions form a second PN junction diode.