Method for the production of a bulk acoustic wave resonator with a reduced parasitic capacitance

A method for a production of an acoustic resonator including at least a first functional stack and a second functional stack, the first functional stack including at least one first element consisting of a first layer of piezoelectric or dielectric material interposed between two structured electrically conducting layers, a coverage surface of the two structured electrically conducting layers defining a first active zone, the second functional stack including at least one second element consisting of a second layer of piezoelectric material interposed between a first and a second electrode, a coverage surface of the first and second electrodes defining a second active zone, said method including:

• providing the first functional stack including the first layer of piezoelectric or dielectric material as well as both the structured electrically conducting layers associated with each other defining the first active zone,
• forming the first electrode of the second functional stack on the first functional stack, so as to align the first electrode with the first active zone, and forming a first bonding layer of an electrically insulating material on the first electrode,
• providing a part of the second functional stack comprising at least one second bonding layer of an electrically insulating material and the second layer of piezoelectric material,
• assembling the first functional stack and the part of the second functional stack comprising at least one second bonding layer and the second layer of piezoelectric material by contacting the first and at least one second bonding layers,
• forming the second electrode of the second functional stack, so as to define the second active zone in alignment with the first active zone.