To provide a step-up circuit that generates a voltage higher than an external power supply voltage and a semiconductor device using the step-up circuit.

The step-up circuit comprises a first transistor, a second transistor, a first capacitor, a second capacitor, a diode, and an inverter. One electrode of the first transistor comes to be a prescribed potential. The output side of the inverter is connected to the gate electrode of the first transistor and one electrode of the second transistor through the second capacitor. The input side of the inverter is connected to the other electrode of the first transistor and the gate electrode of the second transistor through the first capacitor. The diode is connected between the other electrode of the first transistor and the other electrode of the second transistor in forward direction.