Using flattened SiO_2/Cu-electrode/36〜48°LiTaO_3 structure, small size (5×5mm^2) surface acoustic wave (SAW) duplexer with a good temperature coefficient of frequency (TCP) for US-PCS was realized. However, smaller duplexer has been strongly required. Using flip-chip bonding process and flattened SiO_2/Cu-electrode/128°YX-LiNbO_3, which has larger coupling factor than above-mentioned substrate, smaller sized (3×2.5mm^2) SAW duplexer with a good TCP has been realized.
