There is provided a semiconductor device including bit lines (14) formed in a semiconductor substrate (10), insulating film lines (18) located on the bit lines (14) to successively run in a length direction of the bit lines (14), gate electrodes (16) located above the semiconductor substrate (10) between the bit lines (14), and word lines (20) located on the gate electrodes (16) to run in a width direction of the bit lines (14), a trench region (22) formed between the bit lines (14) and the between word lines (20) in the semiconductor substrate, and there is also provided a fabrication method therefor. According to the present invention, it is possible to provide a semiconductor device where elements can be isolated between the word lines (14) and memory cells can be miniaturized, and to provide a fabrication method therefor.