Mask read-only memory and fabrication thereof

A method for fabricating a Mask ROM, comprising the steps of:

• forming a silicon oxide/silicon nitride/silicon oxide (ONO) composite layer on a substrate;
• forming a plurality of gate structures on the ONO composite layer, wherein the ONO composite layer between each gate structure and the substrate serves as a predetermined coding region;
• forming a plurality of bit-lines in the substrate between the gate structures;
• forming a plurality of word-lines over the substrate to electrically connect with the gate structures;
• forming a chemical vapor deposition anti-reflective coating (CVD-ARC) over the substrate;
• forming an inter-layer dielectric layer on the chemical vapor deposition anti-reflective coating (CVD-ARC);
• forming a plurality of coding windows in the inter-layer dielectric layer and the chemical vapor deposition anti-reflective coating (CVD-ARC) over selected predetermined coding regions;
• performing a coding process by using UV light to inject charges into the selected predetermined coding regions with the chemical vapor deposition anti-reflective coating (CVD-ARC) as a mask;
• and
• forming a plurality of plugs in the coding windows.