A semiconductor structure includes a semiconductor mesa situated on a semiconductor substrate, a trap-rich region comprising polycrystalline silicon adjacent to the semiconductor mesa, and a phase-change material (PCM) radio frequency (RF) switch. A heating element of the PCM RF switch is situated over the semiconductor mesa. An interconnect segment coupled to the PCM RF switch is situated over the trap-rich region. Alternatively, a semiconductor structure can include a trap-rich region adjacent to a single crystal region of the semiconductor substrate, where the trap-rich region is formed by implant damaging, and where the heating element of the PCM RF switch is situated over the single crystal region.