Silicon PIN switching diodes and GaAs varactor tuning diodes have demonstrated 100% performance improvements in quality factor Q by using straightforward optimization techniques, device processing innovations and improvements in materials. Analogous design techniques have been applied to both devices, including careful modeling to identify series resistance contributions, and directed process development to reduce these contributions. In both cases, substrate resistance was reduced to a minimum with processes that replaced semiconductor substrate with metal. Total resistance was minimized by analytical calculation to define optimum device geometries.