Semiconductor process variation and reliability aging effect on CMOS VCO performance has been studied. A technique to mitigate the effect of process variations on the performances of nano-scale CMOS LC-VCO is presented. The LC-VCO compensation uses a process invariant current source. VCO parameters such as phase noise and core power before and after compensation over a wide range of variability are examined. Analytical equations are derived for physical insight. ADS and Monte-Carlo simulation results show that the use of invariant current source improves the robustness of the VCO performance against process variations and device aging.