Patent ID: 6683803
Filing Date: 2004-01-27
Classification: G11C

Abstract:
A data storage apparatus with means for storing and retrieving data in respective write and read operations, wherein data are stored in a non-volatile manner as polarization states in ferroelectric memory cells, wherein the memory cells are provided in a passive matrix-addressable array, wherein the memory cells can be individually addressed electrically for write and read operations, the addressing of the memory cell taking place via crossing electrodes of a respectively first and second electrode sets, wherein each electrode set comprises parallel stripe-like electrodes such that the electrodes of the first set substantially are oriented orthogonally to the electrodes of the second set, characterized in that the first set of electrodes (a) comprises a plurality of parallel trenches (3) extending horizontally with an orthogonal orientation to the electrodes (a) and vertically downwards from a top surface thereof for a distance less than the thickness of the electrodes (a) and having a substantially rectangular profile, that at least a ferroelectric or electret memory material (2) is provided in the trenches (3) and covering the sidewalls thereof, that the second set of electrodes is provided as a dual set of electrodes, each comprising parallel twin electrodes (b, c) provided in said trenches (3) and parallel therewith and without mutual contact with the electrodes (a) of said first set, that the ferroelectric material (2) is provided in at least a portion of the volume of the trenches (3) not occupied by the electrodes (b, c), said ferroelectric or electret material being a soft or elastic ferroelectric or electret material with piezoelectric properties and in addition providing electrical insulation between the electrodes (b, c) of the second set and the electrodes (a) of the first set, whereby the twin electrodes (b, c) of the second set under a suitably applied force can be displaced laterally in the soft ferroelectric or electret material (2) with piezoelectric properties such that a piezoelectric effect is generated therein, and that said soft ferroelectric or electret material with piezoelectric properties in the volumes between the twin electrodes (b, c) of the second set and the electrodes (a) of the first set forms subcells (&agr;1, &agr;2) of the memory cells (1) in said trenches (3), said subcells (&agr;1,&agr;2) capable of being poled for a write operation by applying an electric field between respective twin electrodes (b; c) and crossing electrodes (a) of the first set, such that the memory cells (1) are polarized to store at least one of two or more logical values in the form of a set of polarization states in said subcells (&agr;1, &agr;2) and can be read non-destructively by applying a voltage potential between the twin electrodes (b, c), and/or between at least one of the latter and at least one of proximal electrodes (a) of the first electrode set, and over ferroelectric or electret material of the subcells (&agr;1, &agr;2) which are subjected to tensile and/or compressive stresses enabling the detection of parameters deriving from the polarization states thereof by means of piezoelectric effects in response to strains thus induced in said subcells, whereby the logic state of the subcells (&agr;1, &agr;2) of a memory cell (1) can be found and the logical value or values stored in a memory cell (1) containing the subcells (&agr;1, &agr;2) can be determined.