A method of fabricating a dielectric film includes depositing a first precursor on a substrate. The first precursor includes a cyclic carbosiloxane group comprising a six-membered ring. The method also includes depositing a second precursor on the substrate. The first precursor and the second precursor form a preliminary film on the substrate, and the second precursor includes silicon, carbon, and hydrogen. The method further includes exposing the preliminary film to energy from an energy source to form a porous dielectric film.