Aluminum nitride (AlN) thin films have been deposited on silicon (100) wafers by radio frequency reactive magnetron sputtering. The as-deposited AIN films are less dense and have a higher dangling bonds percentage than AIN single crystals. In addition the surface of as-deposited film is too rough to apply to electronic devices. In order to overcome those limitations, nitrogen plasma treatment (NPT), as a novel heat-treatment, is used for the first time in this work. As NPT time increases, surface roughness is dramatically reduced and, at the same time, the Al-N bonds in the films become stable. As a result, chemical stability of nitrogen-plasma-treated AlN films increases sharply in a strongly alkaline solution, 2 M KOH. Furthermore, the interactions between AIN films and nitrogen plasma result in the improvement of electrical properties of AIN films, i.e., the leakage current density measured by I-V method is reduced. (C) 2000 The Electrochemical Society. S0013-4651(00)02-048-6. All rights reserved.