A CMOS inverter is provided. The CMOS inverter includes a substrate. The CMOS inverter also includes an NMOS transistor having a first active region, a first isolation structure surrounding the first active region, a first connect structure, a plurality of the first metal interconnect structure and a first shunted gate structure to reduce a delay time and increase a saturation current. Further, the CMOS inverter includes a PMOS transistor having a second active region with a reduced area to reduce the delay time and increase the saturation current, a second isolation structure surrounding the second active region, a second connect structure, a plurality of metal interconnect structure and a second gate structure connecting with the first gate structure through the first connect structure and/or the second connect structure.