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A 90-GHz LC-resonator based voltage-controlled oscillator (VCO) is fabricated in a 130-nm foundry CMOS process. The core transistor structure has been optimized to reduce parasitic capacitances. An accumulation mode MOS varactor has been optimized to achieve Q of ∼7 at 90 GHz or ∼600 at 1 GHz. The VCO is tuned by changing the bias voltage of current source transistor, which modifies the DC bias for core transistors, and that for the varactors to achieve a tuning range of 2.2 GHz. The VCO core consumes 5 to 10.5-mA current from a 1.5-V supply. The phase noise at 10-MHz offset from carrier varies between -104 to -106 dBc/Hz over the tuning range.