A flip-flop (FF) includes a first n-channel metal oxide semiconductor (NMOS) transistor connected to a ground line, a first p-channel metal oxide semiconductor (PMOS) transistor connected to a power voltage line, a second NMOS transistor connecting a first node to the first NMOS transistor, a second PMOS transistor connecting the first node to the first PMOS transistor, a third NMOS transistor and a fourth NMOS transistor, connected to the second NMOS transistor in parallel, and forming a first discharge path for connecting the first node to the ground line, a third PMOS transistor and a fourth PMOS transistor, connected to the second PMOS transistor in parallel, and forming a first charge path for connecting the first node to the power voltage line, a keeper circuit connected to the first node to maintain a voltage level of the first node.