A design method places power gates or switch cells using unoccupied locations of logic cell rows. Two types of such switch cells, filler switches and sealer switches, may be provided using the unoccupied locations. In one embodiment, virtual ground voltage references to the logic cells are routed to their associated switch cells. Because conventional standard cell design and placement techniques achieve only a placement density or utilization between 70-80% (i.e., unoccupied space constitutes between 20 to 30% of the available space in each row of logic cells), by placing the power gate cells in the unoccupied space, the method does not increase the silicon real estate requirement even though the power gate cells are introduced into the design. Optimization techniques may be applied to achieve proper sizing and distribution of power gate cells, so as to avoid a performance penalty due to the power gate cells. In one embodiment, fine-grained power gating is achieved by selectively providing non-power-gated logic cells among power-gated logic cells.