A chemical vapor deposition method for forming an aluminum-silicon nitride layer upon a substrate uses an aluminum precursor, a silicon precursor and a nitrogen precursor under chemical vapor deposition conditions to deposit the aluminum-silicon nitride layer upon the substrate. The aluminum-silicon nitride layer has an index of refraction interposed between silicon nitride and aluminum nitride. The aluminum-silicon nitride layer also has a bandgap from about 4.5 to about 6 eV and a permittivity from about 6×10̂-11 to about 8×10̂-11 F/m. The aluminum-silicon nitride layer may be further thermally annealed to reduce a hydrogen content of the aluminum-silicon nitride layer.