We employed a-C:H buffer layer to improve the crystalline property of ZnO thin film for the membrane film bulk acoustic resonator (FBAR). The a-C:H film as a buffer layer is prepared by applying dc bias of 200 V and also this sample showed a smoother surface roughness, higher hardness and Young's modulus when compared to the other samples. In addition, the FWHM value was improved from 7.5 to 4.3 degrees on a-C:H film. The fabricated FBAR device showed the resistivity of 0.73 x 10(8) Omega when compared with no buffer layer and the frequency characteristics of the FBAR were finally confirmed to be 1.15 GHz and 21.24 dB, respectively. (c) 2006 Elsevier B.V. All rights reserved.