The present disclosure relates to a method of forming a FinFET device having sidewalls spacers comprising an air gap that provides for a low dielectric constant, and an associated apparatus. In some embodiments, the method is performed by forming a fin of semiconductor material on a semiconductor substrate. A gate structure, having a gate dielectric layer and an overlying gate material layer, is formed at a position overlying the fin of semiconductor material. Sidewall spacers are formed at positions abutting opposing sides of the gate structure. Respective sidewall spacers have a first layer of insulating material abutting the gate structure and a second layer of insulating material separated from the first layer of insulating material by an air gap. By forming the FinFET device to have sidewall spacers with air gaps, the parasitic capacitance of the FinFET device and a corresponding RC time delay are decreased.