Three-dimensional memory device including capped molybdenum word lines and method of making the same

A method of forming a three-dimensional memory device, comprising:

• forming a combination of an alternating stack of insulating layers and molybdenum layers and memory openings vertically extending through the alternating stack over a substrate;
• selectively forming a vertical stack of conductive capping material portions within each of the memory openings directly on physically exposed surfaces of the molybdenum layers;
• and
• forming a memory opening fill structure within each of the memory openings, wherein the memory opening fill structure comprises a vertical semiconductor channel and a memory film comprising a metal oxide blocking dielectric layer located in contact with the vertical stack of conductive capping material portions.

A method of forming a three-dimensional memory device, comprising:

• forming a combination of an alternating stack of insulating layers and silicon nitride sacrificial material layer and memory openings vertically extending through the alternating stack over a substrate;
• selectively forming a vertical stack of ruthenium capping material portions within each of the memory openings directly on physically exposed surfaces of the sacrificial material layers;
• forming a memory opening fill structure within each of the memory openings, wherein the memory opening fill structure comprises a vertical semiconductor channel and a memory film comprising a metal oxide blocking dielectric layer located in contact with the vertical stack of conductive capping material portions;
• and
• replacing the sacrificial material layers with molybdenum layers which contact the vertical stack of ruthenium capping material portions.