Non-volatile memory device and manufacturing method and operating method thereof

A method for fabricating a non-volatile flash memory device, the method comprising:

• providing a substrate;
• forming a first conductive type first well region in the substrate;
• forming a second conductive type second well region above the first conductive type first well region;
• forming a trench in the substrate, wherein a depth of the trench is greater than a depth of the second conductive type second well region;
• forming a composite dielectric layer at both sides of the trench, wherein the composite dielectric layer comprises a charge storage layer;
• forming a pair of conductive spacers on sidewalls of the trench, wherein the composite dielectric layer is disposed between the conductive spacers and the sidewall of the trench;
• and
• forming a source region and a pair of drain regions in the substrate, wherein the source region is formed in the substrate between two of the neighboring conductive spacers, and the drain regions are formed on two sides of the trench in the second conductive type second well region.