The present invention provides semiconductor device and a fabrication method therefor. The semiconductor device includes trenches (11) formed in a semiconductor substrate (10), first ONO films (18) provided on both side surfaces of the trenches, and first word lines (22) provided on side surfaces of the first ONO films (18) and running in a length direction of the trenches (11). According to the present invention, it is possible to provide a semiconductor device and a fabrication method therefor, in which higher memory capacity can be achieved.