Effect of Geometry Aspect Ratio on Elliptical Gate-All-Around SONOS Nanowire

We have investigated characteristics of cylindrical Gate-all-around (GAA) SONOS memory cell with an elliptical cross-section by 3D TCAD simulation since cross-sections of most fabricated Gate-All-Around SONOS memory cells are elliptical not circular. Because of properties of an ellipse, curvature around the elliptical SONOS cell is not uniform, which gives electric field difference between the gate stacks of major and minor axes of a cell. Thus, when the elliptical SONOS cell is turned on, channel current is not evenly distributed around the silicon body and it has a vital effect on the program efficiency.