A method of forming a boron nitride or boron carbon nitride dielectric produces a conformal layer without loading effect. The dielectric layer is formed by chemical vapor deposition (CVD) of a boron-containing film on a substrate, at least a portion of the deposition being conducted without plasma, and then exposing the deposited boron-containing film to a plasma. The CVD component dominates the deposition process, producing a conformal film without loading effect. The dielectric is ashable, and can be removed with a hydrogen plasma without impacting surrounding materials. The dielectric has a much lower wet etch rate compared to other front end spacer or hard mask materials such as silicon oxide or silicon nitride, and has a relatively low dielectric constant, much lower then silicon nitride.