Advanced nor-type mask ROM

A NOR-type mask ROM having a cell array region, an interface region, and a peripheral region, the NOR-type mask ROM comprising:

• a semiconductor substrate of a first conductivity type;
• a plurality of buried diffusion regions of a second conductivity type opposite to the first conductivity type, arranged in parallel on the substrate to serve as sources and drains;
• a plurality of channel regions defined between the buried diffusion regions, the channel regions being of the first conductivity type and defined in the cell array region;
• a plurality of gate insulating layers formed on the channel regions;
• a plurality of gate regions formed in parallel on the gate insulating layers, intersecting the buried diffusion regions, and overlapping with the channel regions, to serve as word lines;
• an insulating layer formed on the overall surface of the substrate, covering the gate regions;
• a plurality of sub-gate regions formed into spacers on the sidewalls of the insulating layer, in parallel with the gate regions, wherein
• the plurality of buried diffusion regions comprises
• a plurality of first buried diffusion regions of the second conductivity type arranged in parallel on the substrate to serve as sources and drains at both sides of the channel regions in the cell array regions, and
• a plurality of second buried diffusion regions formed into islands isolated by a plurality of field oxide films in the interface region, and
• the plurality of gate insulating layers are formed on the first and second buried diffusion regions in the cell array region and the interface region;
• a metal word line extended from the peripheral region, for supplying a voltage to the gate regions;
• and
• a butted contact formed across the gate regions and the second buried diffusion regions through the insulating layer in the interface region, for connecting the metal word line to the second buried diffusion regions and the gate regions.