Plasma-enhanced atomic layer deposition (PEALD) of ruthenium thin films was performed using an alternate supply of bis(ethylcyclopentadienyl)ruthenium [Ru(EtCp)(2)] and NH3 plasma. NH3 plasma acted as an effective reducing agent for Ru(EtCp)(2). The ruthenium film formed during one deposition cycle was saturated at 0.038 nm/cycle, and its resistivity was 12 muOmega cm. No carbon or nitrogen impurities were incorporated in the film as determined by elastic recoil detection time of flight. The film density was higher than that formed by a conventional ALD, in which oxygen was used. The root-mean-square surface roughness of a 50 nm thick PELAD ruthenium film was 0.7 nm. (C) 2004 The Electrochemical Society.