Film bulk acoustic resonator, filter circuit and method for manufacturing a film bulk acoustic resonator

A filter circuit using a plurality of electrically connected film bulk acoustic resonators on a substrate, each of the film bulk acoustic resonators comprising:

• a bottom electrode provided on a surface of the substrate having a cavity at the surface of the substrate so as to extend over the cavity;
• a piezoelectric film disposed on the bottom electrode;
• a top electrode disposed on the piezoelectric film so as to face the bottom electrode and extending over the surface of the substrate;
• and
• a seal member configured to seal a capacitor defined by the bottom electrode, the piezoelectric film and the top electrode, and to provide an opening portion of the cavity outside the seal member at the surface of the substrate.

A method for manufacturing a film bulk acoustic resonator, comprising:

• selectively forming a sacrificial film in and at a surface of a substrate;
• delineating a bottom electrode on the surface of the substrate so as to extend over the sacrificial film;
• delineating a piezoelectric film on the bottom electrode;
• delineating a top electrode on the piezoelectric film so that a part of the top electrode faces the bottom electrode and another part of the top electrode extends over the surface of the substrate;
• forming a support member on the substrate so as to surround a capacitor defined by the bottom electrode, the piezoelectric film and the top electrode and to locate a portion of the sacrificial film outside a surrounded region of the support member;
• attaching a seal plate on the support member above the capacitor so as to seal the capacitor;
• and
• forming a cavity at the surface of the substrate by removing the sacrificial film through the portion of the sacrificial film located outside the surrounded region of the support member.