15 nm Planar Bulk SONOS-type Memory with Double Junction Tunnel Layers using Sub-threshold Slope Control

15 nm gate length bulk-planar SONOS-type memory device, which has Si nanocrystal layer lying between double tunnel oxides, retains 2.7 decades memory window for 10 years below 10 V write / erase (w/e) voltages. S-factor is controlled by source/drain (S/D) junction depth and channel concentration. It is experimentally shown that S to D direct tunneling determines a physical limit of S-factor control below 15 nm scale. Further device scaling and improvement by Si nanocrystal scaling are possible within the limit of S-factor control.