An IC (“integrated circuit”) chip includes a substrate and a phase-change material (PCM) radio frequency (RF) switch, having a heating element, a PCM situated over the heating element, and PCM contacts situated over passive segments of the PCM. The heating element extends transverse to the PCM and underlies an active segment of the PCM. An active device is situated in the substrate. In one approach, the PCM RF switch is situated over the substrate, and the substrate is a heat spreader for the PCM RF switch. In another approach, the PCM RF switch is situated in or above a first metallization level, and a dedicated heat spreader is situated under the PCM RF switch. Alternatively, a PCM RF switch is situated in a flip chip, an active device is situated in the IC chip, and the flip chip is situated over the IC chip forming a composite device.