The semiconductor integrated circuit device includes load circuits and internal voltage generators for generating internal source voltages for driving the load circuits. Each of the internal voltage generators includes a reference voltage generating circuit for generating reference voltages, and regulator circuits for generating the internal source voltages with reference to the reference voltages. The regulator circuit is formed over an SOI substrate and includes a preamplifier circuit for detecting and amplifying a difference between each of the internal source voltages and each of the reference voltages, a main amplifier circuit for amplifying the output of the preamplifier circuit and generating a control signal, and a driver circuit for generating the internal source voltage in response to the control signal. An input stage of the main amplifier circuit is configured by MOS transistors coupling the gates and bodies of the MOS transistors.