A method includes designing a first layout of gate structures and diffusion regions of a plurality of active devices, identifying an edge device of the plurality of active devices, modifying the first layout resulting in a second layout, performing a design rule check on the second layout, and fabricating, based on the second layout, at least one of a photolithography mask or at least one component in a layer of a semiconductor device. Modifying the first layout includes adding a dummy device next to the edge device, adding a dummy gate structure next to the dummy device and extending a shared diffusion region to at least the dummy device. The dummy device and the edge device have the shared diffusion region. Performing the design rule check considers a gate structure of the dummy device as one of two dummy gate structures next to the edge device.