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. Tnt: 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 A1/Ta2O5/Si metal oxide semiconductor structures. The I-V characteristics of both as-deposited and annealed Alms 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.