An inner gate as enabler for vertical pitch scaling in macaroni channel gate-all-around 3-D NAND flash memory

Scaling the vertical cell pitch to increase bit density in 3-D NAND flash memories degrades both the cell transistor characteristics and the memory operation. Here, we therefore investigate an inner gate to mitigate the scaling impact in macaroni channel devices. We evaluate several scenarios with varying complexity using calibrated TCAD simulations: from keeping the inner gate voltage grounded to coupling it to the read gate. We find a trade-off between improved cell transfer characteristics and program voltage determined by the inner gate to read gate coupling ratio.