In a non-volatile semiconductor memory device typically of a MONOS type storing data by trapping charge in a multilayer film composed of a plurality of insulating films, which includes: source and drain regions of a second conductivity type disposed apart from each other in a semiconductor substrate of a first conductivity type; and a multilayer film composed of a plurality of insulating films and disposed on top of a channel region between the source and drain regions, a heavily doped region higher in impurity concentration than the semiconductor substrate is provided in part of the channel region to be in contact with only one of the source and drain regions, and in an uppermost top oxide film of the multilayer film on the channel region, only a portion overlapping with the heavily doped region in a plane view is smaller in thickness than the other portion, whereby a stepped portion is formed.