Bulk-acoustic wave resonator and method for manufacturing the same

A bulk-acoustic wave resonator comprising:

• a substrate;
• a membrane layer disposed on the substrate and forming a cavity together with the substrate;
• a lower electrode disposed on the membrane layer and over the cavity;
• a piezoelectric layer disposed on the lower electrode;
• an upper electrode disposed on the piezoelectric layer, and comprising a frame part disposed at an edge of an active area and comprising a thickness that is greater than a thickness of a portion of the upper electrode disposed in a central portion of the active area;
• and
• a frequency adjusting layer disposed on the piezoelectric layer and the upper electrode,
• wherein the frequency adjusting layer is excluded from an inclined surface of the frame part, or a thickness of a portion of the frequency adjusting layer on the inclined surface is less than a thickness of other portions of the frequency adjusting layer,
• wherein a step portion is disposed on a portion of the frequency adjusting layer disposed on the frame part, and
• wherein an end portion of the frequency adjusting layer has a same angle as the inclined surface of the frame part.

A bulk-acoustic wave resonator comprising:

• a membrane layer disposed on a substrate and forming a cavity together with the substrate;
• a lower electrode disposed on the membrane layer and over the cavity;
• a piezoelectric layer disposed in contact with the lower electrode and the membrane layer, and excluded from at least one inclined surface of the lower electrode;
• an upper electrode disposed on the piezoelectric layer, and comprising a frame part disposed at an edge of an active area and comprising a thickness that is greater than a thickness of a portion of the upper electrode disposed in a central portion of the active area;
• and
• a frequency adjusting layer disposed on the piezoelectric layer and the upper electrode,
• wherein the frequency adjusting layer is excluded from an inclined surface of the frame part, or a thickness of a portion of the frequency adjusting layer on the inclined surface is less than a thickness of other portions of the frequency adjusting layer,
• wherein the frequency adjusting layer is disposed on a portion of the piezoelectric layer protruding from the upper electrode, and
• wherein an end portion of the frequency adjusting layer has a same angle as the inclined surface of the frame part.