Embodiments of semiconductor devices (e.g., RF devices) include a substrate, an isolation structure, an active device, a lead, and a circuit. The isolation structure is coupled to the substrate, and includes an opening. An active device area is defined by a portion of the substrate surface that is exposed through the opening. The active device is coupled to the substrate surface within the active device area. The circuit is electrically coupled between the active device and the lead. The circuit includes one or more elements positioned outside the active device area (e.g., physically coupled to the isolation structure and/or under the lead). The elements positioned outside the active device area may include elements of an envelope termination circuit and/or an impedance matching circuit. Embodiments also include method of manufacturing such semiconductor devices.