PURPOSE: To allow the arbitrary setting of voltage levels of an internal power supply by integrating within one chip an internal power cable, a power voltage conversion circuit by which to apply a certain level of voltage to the cable, and a switching transistor by which to apply a first or second external power voltage.

CONSTITUTION: A device is formed by an integrated circuit block 1 consisting of a MISFET whose gate length is short; an internal power cable 2 by which to supply currents from an external power supply to the integrated circuit block; a power voltage conversion circuit 3, connected to another cable, by which to apply a certain level of voltage to this internal power cable 2; and a MISFET 4 serving as a switching transistor which applies a voltage Ve from the external power supply to the internal power cable 2 while controlling Ve by a switching signal . In the normal operation, a voltage level of the switching signal is set so that the MISFET 4 is in non-conduction, while, to conduct an acceleration test by high voltage operation, it is set so that the MISFET 4 is in conduction, and the external power voltage Ve is applied to the internal power cable 2.