Three-dimensional memory device and method of making thereof using sacrificial material regrowth

A method of forming a memory device, comprising:

• forming a first-tier structure including a first-tier alternating stack of first-tier insulating layers and first-tier sacrificial material layers over a substrate;
• forming a first-tier memory opening through the first-tier alternating stack;
• forming a first-tier sacrificial memory opening fill structure in the first-tier memory opening;
• forming a second-tier structure including a second-tier alternating stack of second-tier insulating layers and second-tier sacrificial material layers over the first-tier structure;
• forming an etch mask layer comprising an opening therethrough over the second-tier alternating stack;
• forming a second-tier memory opening through the second-tier alternating stack, wherein a top surface of the first-tier sacrificial memory opening fill structure is physically exposed underneath the second-tier memory opening;
• removing the etch mask layer employing an etch mask removal process that collaterally removes a top portion of the first-tier sacrificial memory opening fill structure;
• forming a sacrificial pillar structure by performing a selective material deposition process that grows a sacrificial fill material from a top surface of a remaining portion of the first-tier sacrificial memory opening fill structure while suppressing growth of the sacrificial fill material from physically exposed surfaces of the first-tier alternating stack and the second-tier alternating stack;
• forming an inter-tier memory opening by removing the first-tier sacrificial memory opening fill structure and at least a central portion of the sacrificial pillar structure;
• forming a memory opening fill structure in the inter-tier memory opening, wherein the memory opening fill structure comprises a vertical stack of memory elements that are formed at levels of the first-tier sacrificial material layers and the second-tier sacrificial material layers;
• and
• replacing the first-tier sacrificial material layers and the second-tier sacrificial material layers with electrically conductive layers.