An IC device includes first and second power rails extending in a first direction and carrying one of a power supply or reference voltage, a third power rail extending between the first and second power rails and carrying the other of the power supply or reference voltage, and a plurality of transistors including first through fourth active areas extending between the first and second power rails, a plurality of gate structures extending perpendicularly to the first direction, and first and second conductive segments extending in the second direction across the third power rail. Each of the second and third active areas is adjacent to the third power rail, each of the first and second conductive segments is electrically connected to S/D structures in each of the second and third active areas, and the plurality of transistors is configured as one of an AOI, an OAI, or a four-input NAND gate.