Method for fabricating memory device

A method for fabricating a memory device, comprising:

• providing a substrate having an upper surface;
• forming a stacked body on the upper surface of the substrate, wherein the stacked body comprises a first insulating layer, a lower sacrificial layer, a second insulating layer, an upper sacrificial layer and a third insulating layer stacked on the upper surface of the substrate;
• forming a plurality of first openings penetrating the stacked body;
• forming a plurality of lower portions of a plurality of channel structures in the first openings;
• forming a memory layer corresponding to the upper sacrificial layer in each of the first openings;
• forming a plurality of upper portions of the channel structures in the first openings, wherein the upper portions are disposed above the lower portions;
• forming a plurality of second openings penetrating the stacked body;
• removing the upper sacrificial layer and the lower sacrificial layer, and forming an upper opening and a lower opening respectively at positions where the upper sacrificial layer and the lower sacrificial layer are removed;
• filling a conductive material in the upper opening and the lower opening to respectively form a second conductive layer and a first conductive layer, so that a stacked structure comprising the first insulating layer, the first conductive layer, the second insulating layer, the second conductive layer and the third insulating layer is formed;
• and
• forming a plurality of isolation structures in the second openings, the isolation structures separating the stacked structure into a plurality of sub-stacks.