Method for manufacturing a nonvolatile semiconductor memory device having increased hot electron injection efficiency

Abstract

The nonvolatile semiconductor memory device of the present invention includes: a semiconductor substrate having a surface including a first surface region at a first level, a second surface region at a second level lower than the first level, and a step side region linking the first surface region and the second surface region together; a channel region formed in the first surface region of the semiconductor substrate; a source region and a drain region which are formed in the surface of the semiconductor substrate so as to interpose the channel region therebetween; a first insulating film formed on the surface of the semiconductor substrate; a floating gate formed on the first insulating film; and a control gate which is capacitively coupled to the floating gate via a second insulating film. The first insulating film includes a first gate insulating film portion formed in the first surface region, and, a second gate insulating film portion formed in the step side region and the second surface region. The control gate is formed on the first gate insulating film portion. A part of the floating gate faces the step side region via the second gate insulating film portion, and another part of the floating gate is adjacent to the control gate via the second insulating film.