Nucleation and growth of ruthenium films have been studied in temperature ranges of 155-290 degrees C using tricarbonyl[eta(4)-cyclohexa-1,3-diene]ruthenium, ammonia, or nitrous oxide and consecutively pulsed chemical vapor deposition (CVD) conditions. High Ru nuclei surface concentration without nucleation delay was obtained at high deposition temperatures. At low temperatures, surface nucleation was a limiting step of the deposition process. It resulted in a discontinuous film structure with large grains, high surface roughness, and high film resistivity. A shot-time high-temperature pulsed CVD nucleation step and sputtered subnanometer thick metal seed layer allowed significant improvement of ruthenium film morphology. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988062] All rights reserved.