Memory device and method for fabricating same

A memory device, comprising:

• a substrate, a plurality of buried gate structures formed on the substrate, isolation structures, a plurality of conductive word lines in a first direction, and a plurality of active structures arranged at parallel intervals in a second direction;
• wherein the plurality of active structures are island-shaped columnar bodies, the isolation structures are embedded in isolation grooves between the plurality of active structures, and surfaces of the plurality of active structures are flush with surfaces of the isolation structures;
• wherein the plurality of buried gate structures are embedded in the plurality of active structures, and surfaces of the plurality of buried gate structures are flush with the surfaces of the plurality of active structures, and the plurality of buried gate structures are arranged at intervals in the first direction;
• and
• wherein the plurality of conductive word lines are in contact with top surfaces of the plurality of buried gate structures and top surfaces of the isolation structures, and the plurality of buried gate structures arranged along the first direction are electrically connected through a corresponding one of the conductive word lines.

A method for fabricating a memory device, comprising:

• forming a first mask layer on a surface of the substrate;
• patterning the first mask layer to form a plurality of first trenches in the first direction exposing the surface of the substrate;
• etching and removing part of the substrate below the plurality of first trenches using the first mask layer as an etching mask, to form a plurality of embedded word line trenches in the first direction;
• and
• filling a conductive material layer in each of the plurality of embedded word line trenches, such that an upper surface of the conductive material layer is flush with an upper surface of the substrate to form a plurality of buried gate structures;
• patterning the substrate, cutting off the plurality of buried gate structures, and forming a plurality of active structures arranged at parallel intervals and isolation grooves between the plurality of active structures in a second direction, wherein the plurality of active structures are island-shaped columnar bodies, and the plurality of active structures comprise the plurality of remained buried gate structures;
• forming isolation structures in the isolation grooves, surfaces of the isolation structures being flush with surfaces of the plurality of active structures;
• and
• forming a plurality of conductive word lines in the first direction on the top surfaces of isolation structures and the top surfaces of the plurality of active structures, the plurality of conductive word lines covering upper surfaces of the plurality of buried gate structures in the plurality of active structures.