A novel combination of single-electron transistors (SET) with MOS transistors is advanced to create inverter, which, compared with the pure SET circuit, is considerably augmented in its voltage gain and drive capability. Then a close analysis was conducted of the inverter, on the basis of which other logic gates were presented, thus achieving a circuit of two-bit digital comparator. The accuracy of the circuit is verified through the test on SPICE. This hybrid circuit shares the merits with both SET circuit and MOS circuit. Compared with the traditional circuits, this one uses fewer electronic components and is lower in power depletion.