Acoustic resonator comprising temperature compensating layer and perimeter distributed bragg reflector

An acoustic resonator, comprising:

• an acoustic stack arranged over a cavity, the acoustic stack comprising a piezoelectric layer sandwiched between first and top electrode layers and having a main membrane region defined by an overlap between the bottom electrode, the piezoelectric layer, and the top electrode;
• a temperature compensating layer having a positive temperature coefficient for offsetting at least a portion of a negative temperature coefficient of the piezoelectric, the bottom electrode layer and the top electrode layer, the temperature compensating layer being located in one of the bottom electrode layer, the top electrode layer, and the piezoelectric layer;
• a distributed Bragg reflector (DBR) disposed on a substrate around a perimeter of the cavity, the DBR comprising a layer of low acoustic impedance material stacked on a layer of high acoustic impedance material;
• a frame disposed within the main membrane region and having an outer edge substantially aligned with a boundary of the main membrane region;
• and
• a collar disposed outside the main membrane region and having an inner edge substantially aligned with the boundary of or overlapping the main membrane region.