Three-level ferroelectric memory cell using band alignment engineering

A method for switching a memory cell, comprising:

• providing the memory cell in a first polarized state, wherein the memory cell comprises a first ferroelectric layer between a first electrode and a second electrode, and a second ferroelectric layer between the second electrode and a third electrode, at least two of the electrodes have different work functions, and the memory cell is polarizable in at least three polarized states;
• providing a first bias across the memory cell which switches the memory cell from the first polarized state to a second polarized state;
• and
• providing a second bias across the memory cell which switches the memory cell from the second polarized state to a third polarized state;
• wherein:
• in the first polarized state of the memory cell, the first and second ferroelectric layers are in a positive polarized state;
• in the second polarized state of the memory cell, the first ferroelectric layer is in the positive polarized state and the second ferroelectric layer is in a negative polarized state;
• in the third polarized state of the memory cell, the first and second ferroelectric layers are in the negative polarized state;
• the first bias comprise a relatively weak negative bias of the first electrode;
• and
• the second bias comprise a relatively strong negative bias of the first electrode.

A method, comprising:

• providing a memory cell in a first polarized state, wherein the memory cell comprises a first ferroelectric layer between a first electrode and a second electrode, and a second ferroelectric layer between the second electrode and a third electrode, at least two of the electrodes have different work functions, and the memory cell is polarizable in at least three polarized states;
• providing a first bias across the memory cell which switches the memory cell from the first polarized state to a second polarized state;
• and
• providing a second bias across the memory cell which switches the memory cell from the second polarized state to a third polarized state, wherein:
• in the first polarized state of the memory cell, the first and second ferroelectric layers are in a negative polarized state;
• in the second polarized state of the memory cell, the first ferroelectric layer is in a positive polarized state and the second ferroelectric layer is in the negative polarized state;
• in the third polarized state of the memory cell, the first and second ferroelectric layers are in the positive polarized state;
• the first bias comprise a relatively weak positive bias of the first electrode;
• and
• the second bias comprise a relatively strong positive bias of the first electrode.