The effects of vacuum and inert gas annealing of ultrathin (similar to 20 Angstrom) tantalum pentoxide (Ta2O5) films deposited on Si(100), with and without nitrogen passivation, were examined. Without nitrogen passivation, annealing Ta2O5 to 820 degrees C for 10 min led to oxidized silicon at both the Si-Ta2O5 and Ta2O5-vacuum interfaces and some tantalum silicide formation at the Si-Ta2O5 interface. Nitridation inhibited these processes.