SH Surface Acoustic Wave Device Spurious Response Suppression

The single hard dielectric layer is segmented into a three-layer structure consisting of a first dielectric layer (hard dielectric), a second dielectric layer (intermediate acoustic velocity), and a third dielectric layer (soft dielectric). This segmentation allows each layer to serve different functions: the first layer increases acoustic velocity, while the second and third layers suppress spurious responses by creating acoustic impedance gradients that confine the surface acoustic wave energy.

Different regions of the dielectric structure are assigned different acoustic velocities and impedances. The first dielectric layer has high acoustic velocity to boost frequency, while the second and third layers have progressively lower acoustic velocities to create a gradient that confines the acoustic energy locally at the piezoelectric film interface, preventing the generation of spurious wave modes.

The dielectric structure is divided into three distinct layers with different acoustic velocity characteristics. This segmentation creates a controlled acoustic environment that guides the surface acoustic wave propagation, preventing energy concentration that would lead to higher-order modes and plate waves while maintaining the increased acoustic velocity benefit.

The second dielectric layer with intermediate acoustic velocity acts as an intermediary between the high-acoustic-velocity first layer and the low-acoustic-velocity third layer. This intermediate layer serves as a transition zone that smoothly gradients the acoustic impedance, preventing abrupt changes that would cause wave mode conversion and complexity.