Electronic system device and method of starting the same

An electronic system device comprises a power generation device generating a power supply voltage, a substrate bias generation circuit connected to the power generation device, a memory circuit, a monitor circuit, and a capacitor connected to the substrate bias generation circuit via a switch. The substrate bias generation circuit generates a substrate bias voltage from the power supply voltage and supplies charges based on the substrate bias voltage to the capacitor while the switch is ON-state. While the switch is OFF-state, the capacitor stores the accumulated charges based on the substrate bias voltage. While the switch is ON-state, the substrate bias generation circuit adds based on the substrate bias voltage to charge that was held, and states the back bias voltage. The substrate bias generation circuit supplies the back bias voltage to memory circuit.