Reliability improvement in planar MONOS cell for 20nm-node multi-level NAND Flash memory and beyond

20 nm-node planar MONOS cell which has improved reliability is developed. Extremely wide program/erase Vth window and good retention characteristics after cycling stress are obtained by buried charge cell structure. Moreover, Vth shift by interference between adjacent cells has smaller dependence on the cell-cell space than Vth window improvement when the half pitch is constant. These results show that the buried charge planar MONOS cell is suitable for Flash memory with 20 nm-node and beyond.