Novel resonators to enhance the performance of a Voltage-Controlled-Oscillator (VCO) utilizing single and double ring resonators to improve the loaded-quality (QL) factor of the resonator are introduced, and their effectiveness is demonstrated by designing low-phase-noise (PN) K-band VCO. Also, the size of the double-ring-resonator (DRR) is compacted by 40% and its QL-factor is increased. The resonators are designed using HFSS. First Complementary-Single-Split-Ring (CSSRR) is designed and optimized to maximize its QL-factor, then three resonators (meander-line-split-ring, double-ring, compacted-double-ring resonators) are studied to increase their QL-factor compared to the CSSRR. The QL-factor of the DRR is 30 ± 1 at 20–60 GHz with a size of 140 µm*90 µm while the compacted-double-ring-resonator (Compacted DRR) has a size of 120 µm*60 µm and its QL-factor is increased by 25% compared to vertical-DRR. The resulting QL-factor of the proposed resonator is improved significantly that, in return, enhances PN. The resonators are designed in 0.18 μm-CMOS technology and used in the VCOs. The VCOs oscillate in the K-band with PN of −111 and −110.4 dBc/Hz@1MHz offset at 21.3 and 23.1 GHz, for the single and double-ring resonators. The VCOs consume 2.2mW resulting in a Figure-of-Merit (FoM) of −193.9, −194.3, and −195dBc/Hz in the case of CSSR, DR, and Compacted DR resonators; respectively. The achieved FoM is 7 dB better than the obtained one using a conventional resonator (without SRR). The VCOs have good harmonic suppression of better than 26 dB between the fundamental and the second harmonic with an output power of −5.9dBm. Finally, the CSSRR and Compacted DRR VCOs have a core area of 0.031 mm2 and 0.021 mm2, respectively.