FBAR Cavity Structure to Minimize Parasitic Electrode Overlap

The patent segments the electrode structure by introducing a cavity that divides the electrode area into an effective area (within the cavity) and a non-effective area (outside the cavity). This segmentation allows the effective area to contribute to the Q factor and electromechanical coupling coefficient while minimizing the non-effective area that generates parasitic capacitance. The cavity acts as a spatial separator that optimizes the functional distribution of the electrode area.

The patent applies local quality by creating raised structures at specific locations (edges of the cavity) that locally enhance the electrode area for effective coupling while controlling the overall overlap. The raised structures provide localized improvement in electrical connection quality without proportionally increasing parasitic capacitance, as they are positioned to maximize effective area utilization.

The patent introduces a vertical dimension by creating raised structures that extend upward from the substrate surface at the cavity edges. This dimensional change allows the electrode area to be increased in the vertical direction without proportionally increasing the horizontal overlap area that generates parasitic capacitance. The raised structures provide additional effective area for coupling while maintaining control over the parasitic capacitance-generating overlap.

The patent implements a nested structure where the cavity is formed within the substrate, and the raised structures are positioned at the cavity edges. This nesting arrangement allows the effective resonator area to be maximized within the cavity boundaries while the raised structures provide additional coupling area that does not proportionally increase the parasitic overlap, creating a nested optimization of area utilization.