Mask read only memory device and fabrication method thereof

摘要

A mask ROM and a fabrication method thereof are described. The method includes forming a buried drain region in the substrate and forming a gate oxide layer on the substrate. A patterned dual-layer structure dielectric layer is formed on the gate oxide layer. A conductive layer, which is perpendicular to the direction of the buried drain region, is then formed on the gate oxide layer and on the dual-layer structure dielectric layer to form a plurality of code memory cells. The code memory cells that comprise the dual-layer structure dielectric layer correspond to the logic state of "0", while the memory cells that do not comprise the dual-layer structure dielectric layer correspond to the logic state of "1".