A method of forming a resonator includes forming top and bottom dielectric structures over a substrate. A piezoelectric layer is formed between the top and bottom dielectric structures. A bottom electrode is formed between the piezoelectric layer and the bottom dielectric structure, and a top electrode is formed between the piezoelectric layer and the top dielectric structure. A metal layer is formed over the top dielectric structure and is patterned, thereby forming a first contact pad making electrical contact to the top electrode, a second contact pad making electrical contact with the bottom electrode, and a mass bias located over the top dielectric structure.