A semiconductor integrated circuit device includes a semiconductor substrate of a first conductive type, a first well of a second conductive type provided in the semiconductor substrate, a second well of the first conductive type provided in the first well, a third well of the second conductive type provided in the semiconductor substrate, a fourth well of the first conductive type provided in the third well, semiconductor elements constructing a first functional integrated circuit provided in the first and second wells, semiconductor elements constructing a second functional integrated circuit provided in the third and fourth wells, and an internal power source voltage generating circuit provided in the first well. The internal power source voltage generating circuit configured to generate a first internal power source voltage is applied to the first functional integrated circuit and a second internal power source voltage is applied to the second functional integrated circuit.