Baw filter structure and preparation method thereof

A preparation method of a bulk acoustic wave (BAW) filter structure, comprising:

• a step of fabricating a transfer structure (100):
• forming two or more piezoelectric film elements (121) independent of each other on a surface of an epitaxial substrate (110) and forming bottom electrode units (131) on the piezoelectric film elements (121) correspondingly one to one to obtain the transfer structure (100);
• a step of fabricating a bonding structure (200):
• defining two or more resonant regions independent of each other on a supporting substrate (210), covering the resonant regions with bonding units (231), respectively, and electrically interconnecting the bonding units (231) as needed according to a patterning design to obtain the bonding structure (200), wherein a position of each resonant region is axisymmetric to a position of each piezoelectric film element (121);
• and
• a step of transfer bonding:
• reversing upper and lower surfaces of the transfer structure (100) and bonding the bottom electrode units (131) to the resonant regions correspondingly one to one to obtain a BAW structure (300);
• and removing the epitaxial substrate (110), and forming top electrode units (141) on surfaces of the piezoelectric film elements (121) that are in contact with the epitaxial substrate (110) previously.