The invention provides a semiconductor device including an ESD protection circuit with a high ESD protection characteristic. An RC timer included discharge portion including an RC timer formed by a resistor element and a capacitor element and a PLDMOS transistor is formed so as to turn on only when a surge voltage due to static electricity is applied. Furthermore, a noise prevention portion including first and second NMOS off transistors of which the source electrode and the drain electrode are connected is formed. The source electrode of the PLDMOS transistor of the RC timer included discharge portion is connected to a power supply line. The drain electrode of the PLDMOS transistor and the drain electrode of the first NMOS off transistor are connected. The source electrode of the second NMOS off transistor is connected to a ground line.