Surface acoustic wave device and manufacturing method thereof

摘要

There is provided a surface acoustic wave device having an excellent temperature characteristic and an excellent resonance characteristic. A piezoelectric substrate 12 and interdigital electrode portions 13 and 14 are covered with an insulating layer 21 with an insulating thin film 20 interposed therebetween. The piezoelectric substrate 12 is made of LiTaO 3 and the insulating thin film 20 and the insulating layer 21 are made of silicon oxide. By intentionally making the upper surface of the insulating layer 21 flat, the deterioration of propagation efficiency of surface acoustic waves can be suppressed, so that it is possible to reduce increase in insertion loss of a resonator. Since the upper surface 21a of the insulating layer 21 is flat, it is also possible to reduce variation in resonant frequency and anti-resonant frequency due to the temperature change of the surface acoustic wave device.