Membrane transducer structures and methods of manufacturing same using thin-film encapsulation

A method of forming a microshell membrane transducer structure, comprising:

• providing a MEMS region over a substrate, the MEMS region including a MEMS structural layer defining at least one lower transducer capacitor plate over a MEMS sacrificial release layer;
• forming a first sacrificial layer over the lower transducer capacitor plate;
• forming a second sacrificial layer over and in contact with the first sacrificial layer, and then removing a part of the second sacrificial layer over at least a portion of the lower transducer capacitor plate so as to leave only the first sacrificial layer disposed over the portion of the lower transducer capacitor plate with no second sacrificial layer disposed over the portion of the lower transducer capacitor plate;
• forming an upper microshell layer over the first sacrificial layer and lower transducer capacitor plate;
• creating one or more upper release holes in the upper microshell layer;
• and
• removing the first sacrificial layer disposed over the portion of the lower transducer capacitor plate through the upper release holes to form an open area between the upper microshell layer and the lower transducer capacitor plate such that a portion of the upper microshell layer forms a transducer membrane disposed over the open area and underlying lower transducer capacitor plate.