A semiconductor device is provided. Gates of first PMOS and NMOS transistors are coupled together for receiving an input signal. Gates of second PMOS and NMOS transistors are coupled together. Gates of third PMOS and NMOS transistors are coupled together. Gates of fourth PMOS and NMOS transistors are coupled together. Drains of fourth PMOS and NMOS transistors are coupled together for providing an output signal. When the first, second, third and fourth NMOS transistors are connected in parallel and the first, second, third and fourth PMOS transistors are connected in parallel, the output signal is provided according to the input signal and a first logic function. When the first and second NMOS transistors are connected in serial and the first and second PMOS transistors are connected in serial, the output signal is provided according to the input signal and a second logic function.