Bulk acoustic wave resonator, bulk acoustic wave filter, rf module including bulk acoustic wave resonator and/or filter, and bulk acoustic wave oscillator

Abstract

A bulk acoustic wave resonator which has excellent elasticity and high electromechanical energy conversion efficiency. A bulk acoustic wave resonator comprises a substrate, a lower electrode formed on the substrate, an interlayer formed on the lower electrode layer, a piezoelectric layer formed on the interlayer, and an upper electrode layer formed on the piezoelectric layer. Moreover, both the first lattice mismatch, which is determined between a short edge of the lattice constituting a closest packed plane of a material consisting of an interlayer and a short edge of the lattice constituting a closest packed plane of a material consisting of a piezoelectric layer, and the second lattice mismatch, which is determined between a long edge of the lattice constituting a closest packed plane of a material consisting of an interlayer and a long edge of the lattice constituting a closest packed plane of a material consisting of the piezoelectric layer, are 7% or less, and a lower electrode layer is a material in which the value of the elastic stiffness Cis 300 GN/mor more.