Atomic force microscopy was employed to follow the development of Al2O3 films deposited by atomic layer epitaxy (ALE) from AlCl3 and H2O. In contrast to the earlier observations that substantial agglomeration takes place in the beginning of the ALE growth of polycrystalline films, only very small agglomerates were formed during the growth of the amorphous Al2O3 films. Consequently, no pronounced surface roughening took place with increasing film thickness and the resulting films remained much smoother than the polycrystalline films deposited by ALE. Even a 730 nm thick Al2O3 film had a root-mean-square roughness of only 0.7 nm.