PURPOSE: To uniform the data erasing characteristic of each memory cell in semiconductor nonvolatile memory without the degradation in data writing characteristic.

CONSTITUTION: The title semiconductor non-volatile memory consists of a gate insulating film (14) formed on a p-type silicon substrate (10); floating gate (16), coupling insulating film (20) and control gate (22) stacked on the gate insulating film (14); drain region (22) and source region (26) formed by ion implantation using the control gate (22) and a field oxide film as a mask. The phosphorus P concentration of 1×1020/cm3 or below on the source region side of the floating gate (16) prevents the increase in silicon particle size (1μm or below), and thus controls the fluctuation in effective gate insulating film thickness and silicon particle size.