TWI382525B

An electrostatic discharge protection device with a thyristor structure enabling a reduction in layout size and prevention of application of an overvoltage to a semiconductor integrated circuit by a low turn-on voltage when an overcurrent due to electrostatic discharge flows in. The electrostatic discharge protection device comprises a semiconductor substrate (1) of a first conductivity type, a well (2) of a second conductivity type, a first impurity region (6) of the second conductivity type with a higher impurity concentration than the well which is formed on the surface of the semiconductor substrate and serves as one of a cathode and an anode, a first contact impurity region (7) of the first conductivity type with a higher impurity concentration than the semiconductor substrate which is formed on the surface of the semiconductor substrate, a second impurity region (4) of the first conductivity type which is formed on the surface of the well while touching the surface of the well and serves as the other of