Three-dimensional multilevel device containing seamless unidirectional metal layer fill and method of making same

A three-dimensional memory device, comprising:

• a vertical repetition of a unit layer stack including an insulating layer, an electrically conductive layer, and a nucleation promoter layer located over a substrate;
• and
• memory stack structures extending through the vertical repetition, wherein each of the memory stack structures comprises a memory film and a vertical semiconductor channel;
• wherein:
• the vertical repetition of the unit layer stack comprises a terrace region in which each electrically conductive layer other than a topmost electrically conductive layer within the vertical repetition laterally extends farther than any overlying electrically conductive layer within the vertical repetition;
• the terrace region includes stepped surfaces of the vertical repetition that continuously extend from a bottommost layer within the vertical repetition to a topmost layer within the vertical repetition;
• and
• support pillar structures extend through the stepped surfaces and through a retro-stepped dielectric material portion that overlies the stepped surfaces.