In an embodiment, an integrated circuit includes transistors in different active regions, electrically isolated using single diffusion break isolation. The single diffusion break isolation includes a first dummy transistor that has a different threshold voltage than the transistors in either active region for which the single diffusion break is creating isolation. The first dummy transistor may have lower leakage current than transistors in either active region, creating effective isolation between the active regions and consuming relatively small amounts of power due to the lower leakage currents.