Methods for fabricating nonvolatile memory device

A method for fabricating a nonvolatile memory device comprising:

• sequentially forming a first buffer oxide layer and a first buffer nitride layer on a semiconductor substrate;
• removing some portion of the first buffer nitride layer and the first buffer oxide layer to form an opening through the first buffer nitride layer and the first buffer oxide layer;
• forming sidewall floating gates on the sidewalls of the first buffer nitride layer within the opening;
• forming a block oxide layer on the semiconductor substrate including the sidewall floating gates and the first buffer nitride layer;
• sequentially forming a polysilicon layer for a polysilicon main gate and a second buffer nitride layer on the block oxide layer;
• forming a polysilicon main gate by removing some portion of the second buffer nitride layer and the polysilicon layer for a polysilicon main gate;
• forming first sidewall spacers on the sidewalls of the polysilicon main gate and the sidewall floating gates;
• forming common source and drain regions in the semiconductor substrate by performing an ion implantation process;
• depositing and planarizing an insulating layer over the semiconductor substrate so as to fill the gap between the polysilicon main gates;
• depositing a polysilicon layer for a word line over the semiconductor substrate including the insulating layer;
• patterning the polysilicon layer for a word line and the polysilicon main gate in the direction of a word line by removing some portion of the polysilicon layer for a word line and the polysilicon main gate;
• and
• forming second sidewall spacers on the sidewalls of the word line and the polysilicon main gate.