| Radio frequency (RF) filters in high frequency using surface acoustic wave (SAW) such as MediaFLO, Time Division Synchronous Code Division Multiple Access (TD-SCDMA) in China handy phone system, and global positioning system (GPS) in cars require a narrow bandwidth. So, the SAW substrates for their RF filters are also required to have a very excellent temperature coefficient of frequency (TCF) and optimum electro-mechanical coupling factor. Rayleigh wave on a ZnO film/Al-electrode/quartz structures and shear horizontal (SH) type of leaky SAW (LSAW) on a flattened SiO2/high density metal electrodes/36-48YX-LiTaO3 one have good TCF and suitable coupling factor to realize them. On the other hand, large reflection coefficient is required to realize the multi-mode resonator filter. Though the latter has the large reflection coefficient, the farmer has small one. So, in the case of the former structure, authors also attempted to apply a high density metal electrode such as Au electrode instead of Al electrode to realize the large reflection coefficient. As the result, the multi-mode resonator filters composed of a ZnO/high density electrode/quartz and a flattened SiO2/high density electrode/LiTaO3 with good TCF for the RF range have been realized for the first time. |