Three-dimensional memory devices and fabricating methods thereof

Abstract

A memory device includes an alternating layer stack including conductive/dielectric layer pairs stacked in a first direction, a first insulating layer on the alternating layer stack, a thickness of the first insulating layer being larger than a thickness of the dielectric layer, and a channel structure extending through the alternating layer stack and the first insulating layer along the first direction. The channel structure includes an epitaxial layer disposed at a first end of the channel structure away from the first insulating layer, a functional layer on the epitaxial layer and extending along the first direction, a channel layer covering a sidewall of the functional layer and in contact with the epitaxial layer, and a filling structure covering a sidewall of the channel layer. The memory device further includes a channel column structure at a second end of the channel structure near the first insulating layer and in contact with the channel layer, and a top selective gate structure over the first insulating layer and between neighboring channel column structures.