A wideband single-pole single-throw (SPST) switch covering the dc to 220-GHz frequency range is presented in this letter. A four-element distributed topology is used to extend operation to the upper millimeter-wave band. With a combination of front-gate and back-gate biasing, unique to fully depleted silicon-on-insulator (FDSOI) MOSFETs, and enabled by the thick metal/dielectric backend of the technology, the switch achieves an insertion loss of 3.1 dB and an isolation of 37 dB at 220 GHz, as well as a peak isolation of 58 dB at 200 GHz, without deembedding the pads. A $G$ -band variable gain low-noise amplifier featuring the SPST switch shows >50-dB gain control range, with a maximum peak gain of 9.5 dB at 190 GHz and a 3-dB bandwidth from 180 to 203 GHz.
