Al2O3 thin films were deposited on Si substrates by atomic layer deposition (ALD) using Al(CH3)(3) (trimethylaluminum, TMA) as a metal source and (CH3)(2)CHOH (isopropyl alcohol, IPA) as an oxygen source at 250degreesC. The film growth rate is saturated at 0.8 Angstrom/cycle, and it is slightly lower than that for the procedure which uses water vapor instead of IPA. The as-deposited film has a stoichiometry close to Al2O3 (Al/O ratio similar to2:3.1) and the residual carbon content of the films is below the detection limit of secondary ion mass spectroscopy. An interface oxide between the Al2O3 film and Si-substrate was not detectable on the as-deposited film by transmission electron microscopy. However, after annealing at 800degreesC for 5 min, an interface oxide is newly formed even under the neutral ambient of Ar, and it grows thicker under the oxidizing ambient of O-2. That is, oxygen, which is needed for forming the interface oxide during the annealing process is supplied from both of the ambient oxygen and the excess oxygen in the films. Thus, although the loss of dielectric constant is inevitable during the annealing process, it can be minimized by using IPA in Al2O3 ALD.