Plasma-enhanced chemical vapor deposition of aluminum nitride (AlN) films was performed on diamond film substrates using electron cyclotron resonance which have an attractive potential for application such as surface acoustic wave devices operating at high frequency. N-2 and AlCl3 were used as reactant precursors. The dependences of the film morphology, film orientation, deposition rate on the diamond crystal orientation, substrate temperature and microwave power were investigated by scanning electron microscopy, energy dispersive X-ray analysis and X-ray diffraction. c-Axis oriented pure AIN films have been achieved. (C) 2002 Published by Elsevier Science B.V.