This paper demonstrates a metal-organic thin-film encapsulation technique based on the photolithography of multiple layers of positive-tone photo-definable polymer. This encapsulation process, performed at low temperatures (<110 °C) in a standard basic developer, leaves no residue. Piezoelectrically-actuated length-extensional bulk acoustic wave resonators were successfully encapsulated for a proof-of-concept demonstration. Blanket metallization can lead to complete sealing, which helps exclude moisture and particles from sensitive MEMS devices such as high frequency resonators, RF filters and inertial transducers.