Bulk-acoustic wave resonator

A bulk-acoustic wave resonator, comprising:

• a first electrode disposed on a substrate;
• a piezoelectric layer, of which at least a portion is disposed on the first electrode;
• a second electrode disposed on the piezoelectric layer;
• and
• a passivation layer disposed to cover the first electrode and the second electrode,
• wherein either one or both of the first electrode and the second electrode comprise an aluminum alloy layer, and
• either one or both of the piezoelectric layer and the passivation layer have aluminum nitride, or aluminum nitride added with a doping material, configured to have a ratio of an out-of-plane lattice constant “c” to an in-plane lattice constant “a” (c/a) of less than 1.58 and an applied tensile stress of 0 to 500 MPa,
• wherein the aluminum alloy layer contains scandium (Sc) which has a content of 0.1 to 5 at %.