To provide a semiconductor device including: a MOS transistor formed in a semiconductor substrate and have a threshold voltage to be adjusted, a replica transistor of the MOS transistor, a monitoring circuit monitors a gate/source voltage needed when the replica transistor flows a current having a given designed value, a negative voltage pumping circuit generates a substrate voltage of the MOS transistor, based on an output from the monitoring circuit, and a limiting circuit defines the operation of the negative voltage pumping circuit, regardless of a monitoring result of the monitoring circuit, in response to an excess of the substrate voltage with respect to a predetermined value.