A maximum voltage source selector adapted for use in a semiconductor device operative in a disable state or an enable state is disclosed. The maximum voltage source selector includes an output unit having an output node providing a maximum voltage selected from a first input voltage and a second input voltage. First and second gate transistors are commonly coupled to the output node and are respectively configured to select and provide the greater of the first and second input voltages to the output node in response to first and second selection signals without regard to whether the semiconductor device is in the disable state or the enable state. A selection unit generates the first and second selection signals in response to the first and second input voltages.