Highly c-axis-oriented aluminum nitride (AIN) thin films have been prepared on titanium (Ti) bottom electrodes by using AIN interlayers. The AIN interlayers were deposited between Ti electrodes and silicon (Si) substrates, such as AIN/Ti/AIN/Si. The crystallinity and crystal orientation of the AIN films and Ti electrodes strongly depended on the thickness of the AIN interlayers. Although the sputtering conditions were the same, the X-ray diffraction intensity of AIN (0002) and Ti (0002) planes drastically increased, and the full-width at half-maximum (FWHM) of the X-ray rocking curves decreased from 5.1 degrees to 2.6 degrees and from 3.3 degrees to 2.0 degrees, respectively. Furthermore, the piezoelectric constant d(33) of the AIN films was significantly improved from -0.2 to -4.5 pC/N. (c) 2006 Elsevier B.V. All rights reserved.