METHOD OF MAKING ACOUSTIC WAVE DEVICE WITH VERTICALLY MASS LOADED MULTI-LAYER INTERDIGITAL TRANSDUCER ELECTRODE FOR TRANSVERSE MODE SUPPRESSION

A method of manufacturing an acoustic wave device includes forming a multilayer piezoelectric substrate by forming a piezoelectric layer and forming a support substrate below the piezoelectric layer. The method also includes forming an interdigital transducer electrode including forming a first layer disposed over the piezoelectric layer, forming a second layer disposed over the first layer, the second layer being of a less dense material than the first layer, forming a third layer disposed over the second layer. The method also includes etching the third layer to form a pair of strips extending over one or more fingers of the interdigital transducer electrode and having a density that suppresses a transverse mode of the acoustic wave device.