A 3D NAND memory has vertical NAND strings across multiple memory layers above a substrate, with each memory cell of a NAND string residing in a different memory layer. Word lines in each memory layer each has a series of socket components aligned to embed respective floating gates of a group memory cells. This structure allows reduction in cell dimension as well as reducing floating-gate perturbations between neighboring cells. The memory is fabricated by using odd and even subarrays of vertical shafts on a multi-layer slab to create at different times odd and even socket components that overlap to form continuous word lines with socket components. In particular, with only three masks, the even memory cells are fabricated to have their word line socket component enlarged to overlap with those of the odd memory cells in order to form continuous word lines in the row direction.