Methods of fabricating a three-dimensional non-volatile memory device

A method of fabricating a memory device, comprising:

• forming a first stack of alternating layers of a first material and a second material different from the first material over a substrate;
• removing a portion of the first stack to form a first trench;
• filling the trench with a sacrificial material;
• forming a second stack of alternating layers of the first material and the second material over the first stack and the sacrificial material;
• removing a portion of the second stack to the sacrificial material to form a second trench;
• removing the sacrificial material to form a continuous trench through the first stack and the second stack;
• wherein the continuous trench forms a first boundary of an active memory cell area;
• wherein a second continuous trench forms a second boundary of the active memory cell area;
• wherein the active memory cell area comprises a plurality of NAND memory strings extending through the first stack and the second stack, wherein each NAND memory string comprises:
• a semiconductor channel which comprises at least a first portion that extends substantially perpendicular to a major surface of the substrate;
• and
• at least one memory film located adjacent to the semiconductor channel:
• wherein the memory device further comprises a second semiconductor channel portion which extends substantially parallel to the major surface of the substrate above or in the substrate;
• wherein the second semiconductor channel portion is electrically connected to the at least one semiconductor channel in the plurality of NAND strings, and a second memory film portion extends substantially parallel to the major surface of the substrate and is located between the second semiconductor channel portion and a bottom surface of the first and second continuous trenches, the method further comprising:
• etching through the bottom surface of the continuous trenches to expose the second memory film portion;
• forming a sacrificial material over the sidewalls of the continuous trenches;
• and
• etching a portion of the sacrificial material and the second memory film portion at the bottom of the continuous trenches to expose the second semiconductor channel portion.

A method of fabricating a memory device, comprising:

• forming a first stack of alternating layers of a first material and a second material different from the first material over a substrate;
• removing a portion of the first stack to form a first trench;
• filling the trench with a sacrificial material;
• forming a second stack of alternating layers of the first material and the second material over the first stack and the sacrificial material;
• removing a portion of the second stack to the sacrificial material to form a second trench;
• removing the sacrificial material to form a continuous trench through the first stack and the second stack;
• wherein the continuous trench forms a first boundary of an active memory cell area;
• wherein a second continuous trench forms a second boundary of the active memory cell area;
• wherein the active memory cell area comprises a plurality of NAND memory strings extending through the first stack and the second stack, wherein each NAND memory string comprises:
• a semiconductor channel which comprises at least a first portion that extends substantially perpendicular to a major surface of the substrate;
• and
• at least one memory film located adjacent to the semiconductor channel;
• wherein the memory device further comprises a second semiconductor channel portion which extends substantially parallel to the major surface of the substrate above or in the substrate;
• wherein the continuous trenches extend to the second semiconductor channel portion, the method further comprising:
• filling a bottom portion of the continuous trenches with a protective material;
• etching the stack through the continuous trenches to remove the alternating layers of the second material from at least the active memory cell area and form recesses between the alternating layers of the first material;
• forming an electrically conductive material in the continuous trenches and within the recesses to form control gate electrodes adjacent to the memory film in each of the NAND strings;
• and
• removing the electrically conductive material from the continuous trenches.