An IC structure includes a cell, a first rail and a second rail. The cell includes a first and a second active region and a first gate structure. The first and second active region extend in a first direction and is located at a first level. The second active region is separated from the first active region in a second direction. The first gate structure extends in the second direction, overlaps the first and second active region, and is located at a second level. The first rail extends in the first direction, overlaps the first active region, is configured to supply a first supply voltage, and is located at a third level. The second rail extends in the first direction, overlaps the second active region, is located at the third level, separated from the first rail in the second direction, and is configured to supply a second supply voltage.