Filter, duplexer and communication apparatus

A duplexer comprising a transmission filter and a reception filter, the transmission filter and/or reception filter comprise a plurality of piezoelectric thin film resonators,

• the piezoelectric thin film resonators each comprising:
• a substrate;
• a lower electrode disposed on the substrate;
• a piezoelectric film disposed on the substrate and on the lower electrode;
• and
• an upper electrode disposed on the piezoelectric film so as to have a part opposing the lower electrode;
• wherein an electrode region where the upper electrode and the lower electrode overlap each other is shaped to have at least one pair of opposing perimeters that are unparallel to each other;
• any one of the pair of perimeters opposes an electrode region of an adjacent piezoelectric thin film resonator;
• and
• spacing between the perimeter and the opposing perimeter of the electrode region of the adjacent piezoelectric thin film resonator is constant.

A communication apparatus comprising a transmission filter and a reception filter, the transmission filter and/or reception filter comprise a plurality of piezoelectric thin film resonators,

• the piezoelectric thin film resonators each comprising:
• a substrate;
• a lower electrode disposed on the substrate;
• a piezoelectric film disposed on the substrate and on the lower electrode;
• and
• an upper electrode disposed on the piezoelectric film so as to have a part opposing the lower electrode;
• wherein an electrode region where the upper electrode and the lower electrode overlap each other is shaped to have at least one pair of opposing perimeters that are unparallel to each other;
• any one of the pair of perimeters opposes an electrode region of an adjacent piezoelectric thin film resonator;
• and
• spacing between the perimeter and the opposing perimeter of the electrode region of the adjacent piezoelectric thin film resonator is constant.