Two-step l-shaped selective epitaxial growth

A method of processing a semiconductor device having a stack that is formed over a source sacrificial layer above a substrate, a channel structure that extends vertically through the stack and the source sacrificial layer, a gate line cut trench that extends vertically through the stack, and a spacer layer that covers uncovered top and side surfaces of the stack, comprising:

• exposing a lower sidewall of the channel structure by removing the source sacrificial layer;
• forming a protection layer having a first portion that covers the lower sidewall of the channel structure, a second portion that covers the substrate, and a third portion that covers the spacer layer;
• exposing a channel layer of the channel structure by removing the first portion of the protection layer and an insulating layer of the channel structure;
• forming an initial source connection layer over the exposed channel layer of the channel structure;
• exposing the substrate by removing the second portion of the protection layer;
• and
• forming a source connection layer over the initial source connection layer and the exposed substrate.