Resistive random access memory device containing discrete memory material portions and method of making thereof

A method of forming a resistive memory device, comprising:

• forming an alternating stack of insulating layers and electrically conductive layers that extend along a first horizontal direction over a substrate;
• forming laterally recessed regions by laterally recessing sidewalls of the electrically conductive layers relative to sidewalls of the insulating layers;
• forming a conformal barrier material layer in the lateral recessed regions and on the sidewalls of the insulating layers, wherein lateral cavities are present in unfilled volumes of the laterally recessed regions;
• depositing an amorphous precursor memory material layer in the lateral cavities and over the conformal barrier material layer;
• selectively crystallizing portions of the amorphous precursor memory material layer in the lateral cavities into crystalline memory material portions while not crystallizing vertical portions of the amorphous precursor memory material layer on the sidewalls of the insulating layers employing an anneal process;
• removing remaining amorphous portions of the amorphous precursor memory material layer selective to the crystalline memory material portions;
• and
• forming a vertical conductive line on the crystalline memory material portions.