Structure of NROM and fabricating method thereof

A method for fabricating a NROM, comprising the steps of:

• providing a substrate;
• forming a composite dielectric layer on the substrate;
• forming a gate conductive layer on the composite dielectric layer;
• patterning the gate conductive layer and the composite dielectric layer to form a gate structure;
• forming a source/drain extension in the substrate beside the gate structure;
• forming a first spacer on a side-wall of the gate structure, wherein a material of the first spacer has a dielectric constant smaller than 4;
• forming a source/drain region in the substrate beside the first spacer and the gate structure;
• and
• forming a second spacer on a side-wall of the first spacer, wherein a material of the second spacer has an etching rate different from that of the first spacer.

A structure of a NROM, comprising:

• a substrate;
• a stacked gate structure on the substrate;
• a first spacer on a side-wall of the stacked gate structure;
• a second spacer on a side-wall of the first spacer;
• and
• a source/drain region in the substrate beside the stacked gate structure.