Power-handling capability of bulk CMOS-based single-pole double-throw switch operating in millimetre-wave and sub-THz region is significantly limited by the reduced threshold voltage of deeply scaled transistors. A unique design technique based on impedance transformation network is presented in this work, which improves 1-dB compression point, namely P1dB, without deteriorating other performance. To prove the presented solution is valid, a 70-100 GHz switch is designed and implemented in a 55-nm bulk CMOS technology. At 90 GHz, it achieves a measured P1dB of 15 dBm, an insertion loss of 3.5 dB and an isolation of 18 dB. The total area of the chip is only 0.14 mm2.