SAW substrate for Duplexer with Excellent Temperature Characteristics and Large Reflection Coefficient realized by using Flattened SiO2 Film and Thick Heavy Metal Film

Authors previously proposed a SAW PCS-duplexer with an excellent temperature coefficient of frequency (TCF) and a good frequency characteristic composed of a thick-SiO
₂
/thin-Au-electrodes/LiTaO
₃
structure. However, a sheet resistance of thin Au electrode is large, compared with thick Al-electrode, so thin Au-electrode is not suitable for filters requiring low loss. Authors tried to use thick Cu electrodes with small resistance. By flattening large convex portions on the SiO2 surface, a SAW substrate suitable for US-PCS duplexer with low insertion loss and an excellent TCF was realized