Semiconductor integrated circuit having protection elements for preventing mos transistors from plasma damage

Abstract

A semiconductor integrated circuit having protection elements for protecting a MOSFET of a high accuracy analog circuit from plasma damage generated during a manufacture of the semiconductor integrated circuit is provided. The protection elements operate at a lower voltage of PN junction breakdown voltage so as to prevent transistors from degrading or having dielectric breakdown due to plasma damage. A differential amplifier includes first and second n-channel MOS transistors for constructing a differential input pair. A first protection element comprising a plurality of gate-drain connected MOS transistors coupled as a cascade is provided between the gate of the first n-channel MOS transistor and a first differential input terminal. A second protection element comprising a plurality of gate-drain connected MOS transistors coupled as a cascade is provided between the gate of the second n-channel MOS transistor and a second differential input terminal. Each of the first and second protection elements operates at a lower voltage of PN junction breakdown voltage.