The invention provides a 3D NAND memory and a manufacturing method thereof. According to the method, a stacked structure comprising a bottom sacrificial layer, sacrificial
layers and insulating layersis formed on a substrate, the sacrificial
layers and the insulating
layers are alternately stacked on the bottom sacrificial layer, the bottom sacrificial layer is replaced with a source
electrode layer, oxidation treatment is conducted on the source
electrode layer, a first
isolation layer is formed on the surface of the source
electrode layer, and the function of selecting
gate oxide on the back is achieved. The method facilitates control over thickness of the first
isolation layer and improves the uniformity of the first
isolation layer, so that uniform inversion of the source electrode layer is facilitated, and an electronic channel is ensured in read-write operation of the memory. The problems in the thickness and uniformity of the source electrode layer caused by the thickness problem of the back selection
gate oxide layer are solved, and the continuity of a P-type trap and supply of holes in the erasing process can be realized. The source electrode layer is formed in the channel structure in the stacking direction at the same time, the contact area of the source electrode layer and the channel layer is increased, and
electrical connection between the source electrode layerand the channel layer is enhanced.