Trench Self-Aligned EPROM Technology

The cell size of EPROM has been inevitably larger than that of mask ROM because of the necessity of floating gate protrusions over the field oxide. In order to overcome this disadvantage, self-alignment technologies between a floating gate and a field oxide have been previously reported (1)(2). These technologies based on LOCOS like isolation, however, cannot avoid channel width shrinkage due to the bird's beak.