The effects of alkoxy functional groups on atmospheric-pressure chemical vapor deposition (APCVD) using alkoxysilane and ozone are investigated from the standpoint of the molecular structure of the alkoxysilane molecules. Deposition rate and step coverage are evaluated for three kinds of alkoxysilane sources [(RO)(4)Si] : (CH3O)(4)Si, (C2H5O)(4)Si (called TEOS), and ((CH3)(2)CHO)(4)Si. The addition of three kinds of alcohols, CH3OH, C2H5OH, and (CH3)(2)CHOH, to the TEOS/O-3 system is also investigated. Both the deposition rates and step coverage are associated with the RO- functional groups of the alkoxysilane molecule. (CH3O)(4)Si, which contains the smallest alkoxy (RO-) groups, has the highest deposition rate and the best flow characteristics among the three silicon sources. With added alcohol : (i) the OH- group scavenges ozone molecules and affects the deposition rate, and (ii) the RO- group affects only the step coverage. The flow property is also affected by adding RO- fragments in reaction system.