This disclosure provides implementations of electromechanical systems resonator structures, devices, apparatus, systems, and related processes. In one aspect, a sacrificial layer is deposited on an insulating substrate. A lower electrode layer is formed proximate the sacrificial layer. A piezoelectric layer is deposited on the lower electrode layer. An upper electrode layer is formed on the piezoelectric layer. At least a portion of the sacrificial layer is removed to define a cavity such that at least a portion of the lower electrode layer is spaced apart from the insulating substrate.