Acoustic resonator comprising acoustic reflector, frame and collar

A solidly mounted resonator (SMR) device, comprising:

• a substrate;
• a distributed Bragg reflector (DBR) disposed on a top surface of the substrate, the DBR comprising a plurality of acoustic reflector layer pairs;
• an acoustic stack mounted on a top surface of the DBR, the acoustic stack comprising a piezoelectric layer sandwiched between bottom and top electrode layers, and having a main active region defined by an overlap between the bottom electrode, the piezoelectric layer, and the top electrode;
• and
• a collar arranged outside the main active region, the collar defining a collar region having a cutoff frequency that is substantially the same as a cutoff frequency of the main active region.

A solidly mounted resonator (SMR) device, comprising:

• a substrate;
• a distributed Bragg reflector (DBR) disposed on a top surface of the substrate, the DBR comprising a plurality of acoustic reflector layer pairs;
• an acoustic stack mounted on a top surface of the DBR, the acoustic stack comprising a piezoelectric layer sandwiched between bottom and top electrode layers, and having a main active region defined by an overlap between the bottom electrode, the piezoelectric layer, and the top electrode;
• and
• a composite frame arranged inside the main active region, an outer edge of the frame substantially aligned with the boundary of the main active region.