PURPOSE: To provide a semiconductor integrated circuit capable of reducing a chip area of an internal circuit forming region and preventing a latch-up phenomenon in the internal circuit forming region.

CONSTITUTION: A flow of substrate current to the internal circuit from an diffusion element connected to an input terminal or output terminal can be interrupted by forming a diffusion element to be connected to an output terminal or an input terminal at the side (region 2) coming into contact with a region 1 where an input terminal or output terminal is formed, and also forming diffusion elements except the diffusion element formed in the region 2 at the side (region 3) coming into contact with the internal circuit forming region 4 among the diffusion elements constituting the input circuit or output circuit.