Method for fabricating memory device

A method for fabricating a memory device, comprising:

• providing a substrate, wherein the substrate has a first region and a second region;
• forming a plurality of first patterned stack layers in the first region, wherein the first patterned stack layers extend along a first direction, and openings are respectively disposed at two sides of each of the first patterned stack layers;
• forming a filling layer on the first patterned stack layers, wherein the filling layer at least fills into the openings and extend along the first direction form the first region to the second region;
• using the filling layer as mask, removing part of the substrate in the second region, so as to form a plurality of trenches in the substrate in the second region;
• removing the filling layer to expose surfaces of the first patterned stack layer in the first region;
• forming a plurality of buried dielectric layers in the openings between the first patterned stack layers in the first region, and forming a plurality of isolation structures in the trenches in the second region;
• removing portions of the first patterned stack layers to expose surfaces of first conductive layers of the first patterned stack layers;
• and
• forming a second conductive layer extending along a second direction on the substrate, and patterning each of the first patterned stack layers to form a plurality of second patterned stack layers.