The nonvolatile semiconductor memory uses a single floating gate transistor, wherein a control gate electrode (8) is negatively biased while a source region (2) is positively biased, and a writing operation is performed bit by bit by transferring electrons from the floating gate (5) into the source region through Fowler-Nordheim tunneling. And an erasing operation is performed by injecting channel hot electrons from the drain region (3) into the floating gate, or by injecting electrons from a substrate into the floating gate through Fowler-Nordheim tunneling. The source region is connected to an individual bit line, and the drain region to a common line so that over-erasing is averted.