A Mask ROM and a method for fabricating the same are described. The Mask ROM comprises a substrate, a plurality of gates on the substrate, a gate oxide layer between the gates and the substrate, a plurality of buried bit lines in the substrate between the gates, an insulator on the buried bit lines and between the gates, a plurality of word lines each disposed over a row of gates perpendicular to the buried bit lines, and a coding layer between the word lines and the gates.