The piezoelectric and related properties of highly c-axis oriented AlN films fabricated by de planar magnetron sputtering have been measured. Experimental results show that highly c-axis oriented AlN films can be fabricated by dc lanar magnetron sputtering at low electric fields with energetic electrons driven out by a magnetic field to reduce any possible damaging effects resulting from electron bombardments on the growing films, and that the AlN films have a strong microwave piezoelectric effect. A microwave bulk acoustic wave delay line formed by depositing an AW film as the transducer on a z-LiNbO3 substrate as the acoustic wave propagation medium exhibits good performances. The major advantage of such a delay line is that its weight and volume can be made much smaller than that of the conventional delay Lines. The AlN films also have good chemical and dielectric properties, suitable for use as insulation or passivation layers.