A dense boron-based or phosphorus-based dielectric material is provided. Specifically, the present invention provides a dense boron-based dielectric material comprised of boron and at least one of carbon, nitrogen, and hydrogen or a dense phosphorus-based dielectric comprised of phosphorus and nitrogen. The present invention also provides electronic structures containing the dense boron-based or phosphorus-based dielectric as an etch stop, a dielectric Cu capping material, a CMP stop layer, and/or a reactive ion etching mask in a ULSI back-end-of-the-line (BEOL) interconnect structure. A method of forming the inventive boron-based or phosphorus-based dielectric as well as the electronic structure containing the same are also described in the present invention.