A non-volatile memory device includes insulators between floating gates. The insulators each include both a lower trench-fill insulator portion in a trench in the substrate, and an upper protruding portion that protrudes from the substrate. Floating gates extend between the protruding portions of adjacent insulators, and are in contact with the protruding portions of the adjacent insulators. An interpoly dielectric overlies the floating gates, and a control gate overlies the interpoly dielectric. The insulators and the floating gates may make a substantially planar surface for the interpoly dielectric, which may themselves be planar.