Abstract
An out-of-plane sensing device is provided. A proof mass is disposed above a substrate. A frame is disposed on the substrate and encloses the proof mass. At least one spring connects the frame and proof mass. When the proof mass moves toward or away from the substrate, the spring will exert a force on the proof mass to have it come back to its equilibrium position. An electrode extends away from the proof mass and toward the frame. A counter electrode extends away from the frame and toward the proof mass, wherein the projection of the electrode onto the substrate overlaps with that of the counter electrode onto the substrate.