We have improved the Q-factor of a 4.6 nH spiral inductor, fabricated on a standard Si substrate, by more than 60%, by using an optimized proton implantation process. The inductor was fabricated in a 1-poly-6-metal process, and Implanted after processing. The implantation increased the substrate impedance by ∼ one order of magnitude without disturbing the inductor value before resonance. The S-parameters were well described by an equivalent circuit model. The significantly improved inductor performance and VLSI-compatible process makes the proton implantation suitable for high performance RF ICs.