Film bulk acoustic resonator having an air gap and a method for manufacturing the same

A film bulk acoustic resonator, comprising:

• a semiconductor substrate;
• a first resistance layer formed on a surface of the semiconductor substrate, the first resistance layer having a recess;
• a membrane layer formed on the first resistance layer over the recess, thereby forming in the recess an air gap region of the acoustic resonator;
• a first electrode formed on the membrane layer;
• a piezoelectric layer formed on the membrane layer and an exposed portion of the first electrode;
• and
• a second electrode formed on the piezoelectric layer,
• wherein the first resistance layer has a predetermined thickness in the recess.

A method for manufacturing a film bulk acoustic resonator, the method comprising:

• forming a resistance layer on an upper surface of a semiconductor substrate, the resistance layer including a recess;
• filling the recess with a sacrificial material;
• providing a membrane layer on an upper surface of the resistance layer and an upper surface of the sacrificial material;
• forming a first electrode on an upper surface of the membrane layer;
• forming a piezoelectric layer on the upper surface of the membrane layer and on an upper surface of the first electrode;
• forming a second electrode on an upper surface of the piezoelectric layer;
• and
• removing the sacrificial material, thereby forming an air gap between the semiconductor substrate and the membrane layer.