US Patent 11631698 Three-dimensional memory device with ferroelectric material

A method of forming a memory device includes: forming a first layer stack and a second layer stack successively over a substrate, the first layer stack and the second layer stack having a same layered structure that includes a dielectric material, a channel material over the dielectric material, and a source/drain material over the channel material; forming openings that extend through the first layer stack and the second layer stack; forming inner spacers by replacing portions of the source/drain material exposed by the openings with a first dielectric material; lining sidewalls of the openings with a ferroelectric material; forming gate electrodes by filling the openings with an electrically conductive material; forming a recess through the first layer stack and the second layer stack, the recess extending from a sidewall of the second layer stack toward the gate electrodes; and filling the recess with a second dielectric material.