Patent ID: 7367095

Claim:
A method of making an acoustically-coupled transformer, the method comprising: fabricating a first stacked bulk acoustic resonator (SBAR) and a second SBAR, the fabricating comprising: forming lower film bulk acoustic resonators (FBARs) and upper FBARs, each of the FBARs comprising opposed planar electrodes and a piezoelectric element therebetween, the piezoelectric element characterized by a c-axis, the forming comprising setting the c-axes of the piezoelectric elements of the lower FBARs opposite in direction and setting the c-axes of the upper FBARs opposite in direction, and locating an acoustic decoupler between the lower FBAR and the upper FBAR of each SBAR; electrically connecting the lower FBAR of the first SBAR to the lower FBAR of the second SBAR; and electrically connecting the upper FBAR of the first SBAR to the upper FBAR of the second SBAR.