Abstract: A method for forming a memory device includes providing an initial semiconductor structure, including a base substrate; a first sacrificial layer formed on the base substrate; a stack structure, disposed on the first sacrificial layer; a plurality of channels, formed through the stack structure and the first sacrificial layer; and a gate-line trench, formed through the stack structure and exposing the first sacrificial layer. The method also includes forming at least one protective layer on the sidewalls of the gate-line trench; removing the first sacrificial layer to expose a portion of each of the plurality of channels and the surfaces of the base substrate, using the at least one protective layer as an etch mask; and forming an epitaxial layer on the exposed surfaces of the base substrate and the plurality of channels.