A 98/196 GHz low phase noise voltage controlled oscillator (VCO) with a fundamental/push-push mode selector using a 90 nm CMOS process is presented in this letter. An innovative concept of the VCO with the mode selector is proposed to switch the fundamental or second harmonic to the RF output. The VCO demonstrates a fundamental frequency of up to 98 GHz with an output power of greater than -8 dBm. The phase noise of the VCO is better than -100.8∼ dBc Hz at 1 MHz offset frequency, and its figure-of-merit is better than -186∼ dBc Hz. Moreover, the output frequency of the work is up to 196 GHz with a fundamental suppression of greater than -30∼ dBc as the VCO is operated in push-push mode.