Channel structure having tunneling layer with adjusted nitrogen weight percent and methods for forming the same

A method for forming a memory device, comprising:

• forming a channel hole in a stack structure over a substrate;
• depositing, sequentially, a blocking layer and a memory layer radially from a sidewall of the channel hole towards a center of the channel hole;
• after the deposition of the blocking layer and the memory layer, depositing a tunneling layer in direct contact with the memory layer;
• performing a thermal treatment to adjust a nitrogen weight content in the tunneling layer to be no greater than about 28%;
• and
• depositing a semiconductor layer in direct contact with the tunneling layer in the channel hole after the thermal treatment.