ELECTRICALLY ERASABLE, DIRECTLY OVERWRITABLE, MULTIBIT SINGLE CELL MEMORY ELEMENTS AND ARRAYS FABRICATED THEREFROM

The present invention comprises an electrically operated, directly overwritable, multibit, single-cell memory element. The memory element includes a volume of memory material which defines the single cell memory element. The memory material is characterized by: (1) a large dynamic range of electrical resistance values; and (2) the ability to be set at one of a plurality of resistance values within said dynamic range in response to selected electrical input signals so as to provide said single cell with multibit storage capabilities. The memory element also includes a pair of spacedly disposed contacts for supplying the electrical input signal to set the memory material to a selected resistance value within the dynamic range. At least a filamentary portion of the single cell memory element being setable, by the selected electrical signal to any resistance value in said dynamic range, regardless of the previous resistance value of said material. The memory element further includes a filamentary portion controlling means disposed between the volume of memory material and at least one of the spacedly disposed contacts. The controlling means defining the size and position of the filamentary portion during electrical formation of the memory element and limiting the size and confining the location of the filamentary portion during use of the memory element, thereby providing for a high current density within the filamentary portion of the single cell memory element upon input of a very low total current electrical signal to the spacedly disposed contacts.