| abstract |
A method of manufacturing a semiconductor device includes forming a stack of alternating layers comprising insulating layers and spacer material layers over a substrate, forming a memory opening through the stack, forming a layer stack including a memory material layer, a tunneling dielectric layer, and a first semiconductor material layer in the memory opening, forming a protective layer over the first semiconductor channel layer, physically exposing a semiconductor surface underneath the layer stack by anisotropically etching horizontal portions of the protective layer and the layer stack at a bottom portion of the memory opening, removing a remaining portion of the protective layer selective to the first semiconductor channel layer, and forming a second semiconductor channel layer on the first semiconductor channel layer. |