A semiconductor device includes: a first reference voltage generator for generating a first reference voltage; a first band gap circuit for dividing a voltage at a second reference voltage output node to produce a first and a second band gap voltages having a property relative to temperature variations; a first comparator for receiving the first reference voltage as a bias input and comparing the first band gap voltage with the second band gap voltage; and a first driver for pull-up driving the second reference voltage output node in response to an output signal of the first comparator.