This paper presents some methods to improve the resonance characteristics of film bulk acoustic-wave resonator (FBAR) devices. The FBAR devices were fabricated on Bragg reflectors. Thermal treatments were done using sintering and/or annealing processes. The measurement shows a considerable improvement of return loss (S-11) and quality factor (Q(8/p)). These thermal treatments seem very promising for enhancing the FBAR's resonance performance. (c) 2005 Wiley Periodicals, Inc.