A semiconductor device including a first function block operating at a first operation voltage having a first range and for generating a data signal, a second function block operating at a second operation voltage having a second range, and a voltage level control unit for performing or not performing a level shifting operation on a voltage level of the data signal depending on the existence or non-existence of a difference between the first operation voltage and the second operation voltage, and for transmitting a level-shifted data signal or the data signal to the second function block.