Simulation of NOR-Flash Memory Cells Focusing on Narrow Channel Effects on VTH Dispersion

In this paper, we present novel simulation results including threshold voltage (V_TH) dispersions caused by process variations for highly scaled NOR-flash memories. Fully 3-D process and device simulations are applied to calculate both of a cell (or drain) current and an F-N current with a realistic device shape. Owing to the narrow channel effects, not only the cell current but also the F-N current is found to be sensitive to the shapes of an active area and a floating gate. The dependence of the currents on the device shape is strongly related to the degradation of the V_TH dispersion and hence makes it difficult to miniaturize the memory cell. In addition, we propose a suitable cell structure in order to control the V_TH dispersion