Acoustic Resonator with Optimized Outer Perimeter

Example implementations of a bulk acoustic wave resonator with an optimized outer perimeter are disclosed. In an example aspect, a resonator includes a truncated-ellipsoid-shaped active region. The active region includes an outer electrode disposed as a first layer of the active region. The active layer also includes a piezoelectric layer disposed as a second layer of the active region with the piezoelectric layer disposed interior to the outer electrode. The active layer further includes an inner electrode disposed as a third layer of the active region with the inner electrode disposed interior to the piezoelectric layer.