This article proposes an edge-Fowler-Nordheim (FN) tunneling method to make silicon-oxide-nitride-oxide-silicon thin film transistors possess not only 2 bit nonvolatile memory but also transistor switch functions. The 2 bit memory status is determined by measuring drain or source gate-induced drain leakage current, which can be suppressed by hole injection and electron erase after edge-FN tunneling. Because charge injection mainly occurs at the drain or source side during edge-FN tunneling operation, the device retains its transistor switch function without a threshold voltage shift during memory operation.