Cell array region of a NOR-type mask ROM device and fabricating method therefor

A method for forming a cell array region of a NOR-type mask ROM device, the method comprising the steps of:

• forming a gate insulating layer on a semiconductor substrate;
• forming a plurality of word line patterns parallel to one another on the gate insulating layer;
• forming a plurality of sub-bit line patterns which intersect a top portion of the plurality of word line patterns at right angles and contact the semiconductor substrate between the word line patterns;
• etching the semiconductor substrate using the plurality of word line patterns and the plurality of sub-bit line patterns as a self-aligned etching mask to form a plurality of trench regions;
• forming an interlayer insulating layer on the entire surface of the semiconductor substrate on which the plurality of trench regions have been formed;
• patterning the interlayer insulating layer to form bit line contact holes each of which exposes an active region which is connected with a sub bit line forming a sub-bit line pattern;
• and
• forming bit lines which are parallel to each sub-bit line pattern and are electrically connected with each sub-bit line through each bit line contact hole.