Plate mode micro-acoustic filters with suspended electrode fingers and related fabrication methods

Abstract

A micro-acoustic filter includes a piezoelectric layer having a crystalline structure that may be laterally excited in a plate mode. The piezoelectric layer is formed on a layer stack that reflects acoustic energy back toward the piezoelectric layer. Acoustic waves are excited in the piezoelectric layer by voltages provided in interdigital transducers (IDTs) on an exposed surface of the piezoelectric layer. The electrode fingers of the IDTs are spaced from the exposed surface rather than being in contact with the exposed surface of the piezoelectric layer to avoid losses and spurious modes. In some examples, the electrode fingers may be supported on one end in a cantilevered configuration to maintain a first distance from the exposed surface of the piezoelectric layer. In some examples, the electrode fingers may also be supported on a second end by a pillar extending the first distance to the exposed surface.

Dependencies are inferred from the claim text.