A chemical vapor deposition process for depositing dielectric films of aluminum oxynitride is described. AlCl3, CO2 and NH3 were employed as the reactive gases in a nitrogen carrier. Films were grown from the mixed gases at 770 and 900°C in a resistively heated fused silica enclosure. The composition of the films could be varied over the entire range of the pseudobinary AlN-Al2O3 system by controlling the NH3/CO2 gas ratio with an appropriate flow of gaseous AlCl3. Growth rate and index of refraction for the films were obtained using ellipsometric techniques. The film compositions reported were determined by electron microprobe analysis. Film structure, evaluated using transmission electron microscopy, and the electrical properties of the dielectric films have been correlated and are discussed separately in a companion paper entitled, "Some Properties of CVD Films of AlxOyNz on Silicon". © 1975 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.