Patent ID: 8222970

Claim:
A resonant device comprising: a first piezoelectric thin film resonator including, a substrate, a first lower electrode formed on the substrate, a first piezoelectric film formed over the first lower electrode, and a first upper electrode formed on the first piezoelectric film and opposed to the first lower electrode, a second piezoelectric thin film resonator including, a second lower electrode formed above the first upper electrode, a second piezoelectric film formed over the second lower electrode, and a second upper electrode formed on the second piezoelectric film and opposed to the second lower electrode, wherein a first membrane region in which the first lower electrode opposes to the first upper electrode through the first piezoelectric film and a second membrane region in which the second lower electrode opposes to the second upper electrode through the second piezoelectric film are laminated through a second cavity, and wherein the second piezoelectric thin film resonator is mounted directly on the first piezoelectric thin film resonator with the second cavity interposed therebetween such that a portion of at least the second lower electrode of the second piezoelectric thin film resonator that is outside of the second membrane region is anchored directly on a portion of the first piezoelectric thin film resonator outside of the first membrane region.