We report the growth of thin tantalum pentoxide films on Si(100) by photo-assisted chemical vapor deposition (photo-CVD) from a tantalum ethoxide source using an excimer lamp (Xe 2*, 172 nm). The effects of substrate temperature and ultraviolet (UV) annealing on the film formed have been studied using ellipsometry and Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR spectra reveal suboxide formation in the as-deposited films that disappeared after subsequent UV annealing. The electrical properties of the films were determined by capacitance–voltage ( C– V) and current–voltage ( I– V) techniques on Al/Ta 2O 5/Si metal oxide semiconductor structures. The I– V characteristics of both as-deposited and annealed films can be described by the Fowler–Nordheim tunneling mechanism. Dielectric constant values of about 24 were readily achievable in the as-deposited films that are comparable to those obtained by other techniques.