Simulation Analysis and Characteristic Research of High-Performance SAW Devices with Trapezoidal Piezoelectric Structures

The electromechanical coupling factor (K2) is one of the key parameters characterizing the performance of surface acoustic wave (SAW) devices. Conventional SAW structures suffer from a spatial mismatch between mechanical energy and electric fields, which severely limits improvements in K2. To address this limitation, this paper proposes a novel microstructure based on trapezoidal etching of the piezoelectric layer. First, an Al/ZnO/Si trapezoidal etching model was established for simulation studies. The results show that trapezoidal etching reduces mechanical energy leakage and enhances the spatial overlap with electric fields. Subsequently, by varying the bottom width (SZnO), the variation of K2 under three etching shapes (standard trapezoidal, rectangular, and inverted trapezoidal) was investigated. The results indicate that trapezoidal etching significantly enhances K2, which gradually increases as SZnO decreases. Under the theoretical limit (SZnO = 0.1 μm), K2 reaches a maximum of 14.34%, representing a 19-fold improvement over the conventional structure. Simultaneously, the figure of merit (FOM) and insertion loss (S21) are also remarkably improved. Finally, considering practical manufacturing constraints, this paper discusses the configurations of SZnO = 0.2 μm and 0.4 μm, revealing that the performance of the SAW devices remains significantly enhanced in both cases, thereby providing a practically feasible solution for the design and fabrication of high-performance SAW devices.