A dielectric capping layer having a dielectric constant of less than 4.2 is provided that exhibits a higher mechanical and electrical stability to UV and/or E-Beam radiation as compared to conventional dielectric capping layers. Also, the dielectric capping layer maintains a consistent compressive stress upon post-deposition treatments. The dielectric capping layer includes a tri-layered dielectric material in which at least one of the layers has good oxidation resistance, is resistance to conductive metal diffusion, and exhibits high mechanical stability under at least UV curing. The low k dielectric capping layer also includes nitrogen content layers that contain electron donors and double bond electrons. The low k dielectric capping layer also exhibits a high compressive stress and high modulus and is stable under post-deposition curing treatments, which leads to less film and device cracking and improved device reliability.