Filament confinement in reversible resistance-switching memory elements

An apparatus comprising:

• a memory device comprising a first word line, a second word line, a third word line, a first dielectric spacer disposed between the first word line and the second word line, and a second dielectric spacer disposed between the first word line and the third word line, a vertical bit line, a non-volatile memory material disposed between the first word line and the vertical bit line, and a memory cell disposed between the first word line and the vertical bit line, the first word line having a first height, and the non-volatile memory material comprising a uniform thickness between the first word line and the vertical bit line;
• and
• a controller configured to:
• form one or more conductive filaments in the memory cell by applying a first voltage to the first word line, a second voltage to the second and third word lines, and a third voltage to the vertical bit line, wherein the second voltage has a polarity opposite the first voltage, wherein the one or more conductive filaments are substantially confined to a filament region having a second height less than the first height and disposed substantially about a vertical center of the memory cell;
• and
• form an electric field between the first word line and the vertical bit line, wherein the second voltage tunes the electric field to have a substantially maximum value towards the vertical center of the memory cell.