In a semiconductor integrated circuit device, having a pair of voltage step-down power supply circuits for active and standby conditions, a first reference voltage is formed by amplifying a fixed voltage formed in a fixed voltage generating circuit with an amplifying circuit which can adjust the voltage gain having a resistance circuit and a switch controlled with a first trimming switch setting signal. An internal step-down voltage, when the internal circuit is in the active condition, is outputted from a first output buffer, which is activated with a first control signal. A second reference voltage is formed by adjusting a combination of threshold voltages of MOSFETs and a switch controlled with a second trimming switch setting signal; and, an internal step-down voltage, when the internal circuit is in the standby condition, is outputted with a second output buffer, which is activated with a second control signal.