Cavity spanning bottom electrode of a substrate-mounted bulk wave acoustic resonator

A method of fabricating an acoustic resonator comprising:

• forming a layer stack on a substrate such that said layer stack has an interior region that is unsupported and has a first electrode layer that extends from said unsupported interior region to supported peripheral regions at each side of said substrate, said layer stack being formed to include an active layer that is responsive to an applied electrical field to generate acoustic waves and to include a second electrode layer on a side of said active layer opposite to said substrate and said first electrode layer, said layer stack including a piezoelectric layer having an edge portion that extends beyond said first electrode layer and that contacts said substrate.

An acoustic resonator comprising:

• a substrate having an upper surface with an open area;
• an active layer stack on said upper surface and over said open area, said active layer stack including a bottom electrode and a top electrode on opposite sides of a piezoelectric layer, said bottom electrode extending across said open area and connecting to said substrate to provide an unsupported interior region and a supported peripheral region on each major side of said open area, said unsupported interior region being substantially surrounded by said supported peripheral regions, said piezoelectric layer having an edge that extends beyond said bottom electrode, such that said edge resides on said substrate.