Patent ID: 6775173
Filing Date: 2004-08-10
Classification: G11C,H01L

Abstract:
A matrix-addressable apparatus comprising one or more memory devices with multi-directionally switchable memory cells (5) arranged in a passive matrix-addressable array, wherein the memory cells (5) comprises a memory medium in the form of a ferroelectric or electret thin-film memory material capable of being polarized by an applied electric field and exhibiting hysteresis, wherein at least one memory device comprises at least two and not more than three electrode means (E), wherein the first electrode means (E) of said at least one memory device being either the only memory device of the apparatus or the first of two or more memory devices therein, is provided on an insulating substrate (1), and wherein the apparatus is characterized in that the first electrode means (E1) comprises parallel strip-like electrodes (&egr;1) of width w and height h spaced apart and mutually electrically insulated by a portion (2a) of insulating thin-film material provided between the electrodes (&egr;1) and covering the side edges thereof in a layer of thickness &dgr;, said thickness &dgr; being small fraction of the electrode width w, that the electrodes (&egr;1) have a high aspect ratio h/w, that the first electrode means (E1) comprises a plurality of parallel recesses (3) in the top surface thereof and oriented perpendicularly to the longitudinal axis of the electrodes (&egr;1) with a width about equal to the electrode width w and extending downwards from the top surface of the electrodes (&egr;1) to a distance h about one half of the height H of the latter, said recesses (3) being mutually spaced apart by a distance approximately equal to the width w of the electrodes, that at least the side walls of said recesses (3) are covered by a thin film (4a) of the memory material and the bottom surface thereof with the insulating thin film (4b) which optionally also can be formed by the memory material, and that electrodes (&egr;1) of the second electrode set (E2) are provided in the recesses (3) contacting and interfacing the thin-film memory material (4a, 4b) thereof, such that the memory material provided in the recesses (3) forms the memory cell (5) of the memory device, a single memory cell (5) in each case being defined in the volume of the memory material located between an electrode (&egr;1) of the first electrode means and an electrode (&egr;2) of the second electrode means at the crossing thereof, whereby a memory cell (5) can be polarized and switched into lateral directions perpendicular to the side walls of the recess (3) and in a third direction perpendicular to the bottom surface of the recess (3), provided said bottom surface also is covered by the memory material.