Manufacturing method of three-dimensional memory device with improved RC delay

A manufacturing method of a three-dimensional (3D) memory device, comprising:

• forming an alternating sacrificial stack on a substrate, wherein the alternating sacrificial stack comprises first sacrificial layers and second sacrificial layers alternately stacked in a vertical direction;
• forming a vertical structure penetrating the alternating sacrificial stack in the vertical direction, wherein the vertical structure comprises:
• a semiconductor layer elongated in the vertical direction;
• a trapping layer surrounding the semiconductor layer in a horizontal direction;
• and
• a tunneling layer disposed between the semiconductor layer and the trapping layer;
• removing the first sacrificial layers for exposing a part of the vertical structure;
• performing a first etching process after the first sacrificial layers are removed, wherein the trapping layer is etched by the first etching process to include trapping sections aligned in the vertical direction and separated from one another;
• and
• forming insulation layers between the second sacrificial layers, wherein the insulation layers and the second sacrificial layers are alternately stacked in the vertical direction,
• wherein the trapping sections comprises first trapping sections and a second trapping section, the first trapping sections are disposed above the second trapping section in the vertical direction, and the semiconductor layer penetrates through the second trapping section in the vertical direction, wherein the entire second trapping section is completely disposed under the tunneling layer in the vertical direction, and the second trapping section is separated from each of the first trapping sections, wherein one of the insulation layers is directly connected with the second trapping section completely disposed under the tunneling layer in the vertical direction and one of the first trapping sections, wherein a material composition of the one of the insulation layers directly connected with the second trapping section completely disposed under the tunneling layer in the vertical direction is identical to a material composition of the one of the insulation layers directly connected with the one of the first trapping sections.