Bulk acoustic wave resonator, filter and duplexer and methods of making same

摘要

A resonator having a membrane formed of a piezoelectric layer sandwiched between first and second electrode is suspended above a cavity formed from the back surface of the support structure. In one embodiment, the cavity walls are substantially perpendicular to the back surface. In another embodiment, the first electrode is formed in the cavity such that it is electrically connected to an electrode on the back surface of the support structure. In yet another embodiment, the cavity is formed via an etch through via holes in the back surface of the support structure, which leads to greater flexibility in designing a method of manufacture while reducing the need for alignment relative to other designs.