The present invention seeks to provide a non-volatile memory device which has an increased density of storage elements formed thereon. A non-volatile memory device comprises a substrate (2) supporting an array of field efect transistor devices. A plate is movable with respect to the substrate supporting an array of insulated charge storing elements (6) each having gate-forming metal plates (7) adjacent thereto. There is also means (12) for moving the plate with respect to the substrate such that, in use, the plate can be moved to position different charge storing elements over one of the array of field effect transistors so that each field effect transistor is able to determine the charge stored on more than one element. A corresponding magnetic effect device is also provided.