Acoustic wave devices using a piezoelectric thin film resonator have been used as filters and duplexers of wireless devices such as, for example, mobile phones. The piezoelectric thin film resonator has a structure designed to include a lower electrode and an upper electrode facing each other across a piezoelectric film. The region where the lower electrode and the upper electrode face each other across the piezoelectric film is a resonance region. There has been known an art that improves a Q-value by inserting an insertion film into the piezoelectric film as disclosed in Japanese Patent Application Publication No. 2014-161001 (Patent Document 1).
When wiring lines are connected to the upper electrode and the lower electrode of the piezoelectric thin film resonator disclosed in Patent Document 1, the piezoelectric film may degrade, and the characteristics may deteriorate and the reliability may be decreased.