PURPOSE: To provide the internal power source circuit of a semiconductor device capable of supplying a stable internal voltage even when a large current flows transiently in the semiconductor device like the time of changing over addresses.

CONSTITUTION: A capacitor 31 having a large capacitance is connected to the output edge of a boosting circuit 30. The capacitor 31 is charged up to an internal high voltage Vccint2 higher than the internal voltage Vccint by the boosting circuit 30. The drain of an N channel transistor 32 is connected to the output edge of the boosting circuit 30. A voltage Vc being higher than the internal voltage Vccint by the amount of a threshold voltage is supplied to the gate of the transistor 32 and the internal voltage Vccint is outputted from the source of the transistor. When the internal voltage Vccint is lowered, the transistor 32 is made conductive and then the capacitor 31 is discharged via the transistor 32.