Fabrication method of film bulk acoustic resonator (FBAR) filter device

A method for fabricating a film bulk acoustic resonator (FBAR) filter device including at least a first resonator and a second resonator, the method comprising:

• determining a simulation target thickness of each one of a first electrode of the first resonator and a first electrode of the second resonator based on a target performance parameter of the FBAR filter device;
• forming the first electrode of the first resonator and the first electrode of the second resonator on a first surface of a piezoelectric layer, wherein the forming includes:
• forming the first electrode of the first resonator with a thickness that is greater than the simulation target thickness of the first electrode of the first resonator;
• and
• forming the first electrode of the second resonator with a thickness that is the same as the simulation target thickness of the first electrode of the second resonator;
• forming a first passivation layer of each one of the first resonator and the second resonator on a corresponding one of the first electrode of the first resonator and the first electrode of the second resonator;
• forming a second electrode of each one of the first resonator and the second resonator on a second surface of the piezoelectric layer, the second surface being opposite to the first surface;
• forming a second passivation layer of each one of the first resonator and the second resonator on a corresponding one of the second electrode of the first resonator and the second electrode of the second resonator;
• conducting a radio frequency (RF) performance test on the FBAR filter device;
• and
• adjusting a thickness of the second passivation layer of the first resonator based on a result of the RF performance test.