Reaction mechanisms in the atomic layer deposition of Al2O3 from Al(CH3)(3) and water were studied with a quartz crystal microbalance at 150-350 degreesC and with a quadrupole mass spectrometer at 150-400 degreesC. The growth rate was the highest at 250 degreesC. At lower temperatures the growth was limited due to kinetic reasons and at higher temperatures due to lower amount of surface -OH groups. About half of the ligands were released during the Al(CH3)(3) pulse and the other half during the water pulse. The reaction temperature had no marked effect on the growth mechanisms, in the temperature range studied.