The preparation of tin oxide thin films by atomic layer deposition (ALD), using a tetrakis (ethylmethylamino) tin precursor, and the effects of a seed layer on film growth were examined. The average growth rate of tin oxide films was approximately 1.2 to 1.4 A/cycle from 50℃ to 150℃. The rate rapidly decreased at the substrate temperature at 200℃. A seed effect was not observed in the crystal growth of tin oxide. However, crystallinity and the growth of seed material were detected by XPS after thermal annealing. ALD-grown seeded tin oxide thin films, as-deposited and after thermal annealing, were characterized by X-ray diffraction, atomic force microscopy and XPS.