Method for manufacturing three-dimensional memory device

A method for manufacturing a 3D memory device, comprising:

• alternately forming first sacrificial layers and first insulating layers on a substrate;
• forming a first channel through hole penetrating through the first sacrificial layers and the first insulating layers;
• alternatively forming second sacrificial layers and second insulating layers on the first sacrificial layers and the first insulating layers;
• forming a second channel through hole penetrating through the second sacrificial layers and the second insulating layers to be communicated with the first channel through hole;
• forming an initial blocking layer covering surfaces of the first channel through hole and the second channel through hole;
• and
• performing an oxidation treatment to oxidize the initial blocking layer, so as to turn the initial blocking layer into a blocking oxide layer, wherein a gas source for the oxidation treatment comprises a reaction gas and an ionization enhancement gas, the reaction gas comprises hydrogen and oxygen, the ionization enhancement gas comprises a first type ionization enhancement gas and, a second type ionization enhancement gas or a combination of the first type ionization enhancement gas and the second type ionization enhancement gas, the first type ionization enhancement gas comprises at least one in a group consists of tritium, ozone and water, and the second type ionization enhancement gas comprises at least one inert gas.