Nonvolatile semiconductor memory device and method for fabricating the same

摘要

A nonvolatile semiconductor memory device according to the present invention has a control gate electrode (21) which is formed on the upper stage (13) of a stepped portion (16) formed in the principal surface of a substrate with a first insulating film (22) interposed therebetween and a floating gate electrode (23) which is formed to cover up the stepped portion (16), capacitively coupled to the side surface of the control gate electrode (21) closer to the stepped portion (16) with a second insulating film (24) interposed therebetween, and opposed to the lower stage (14) of the stepped portion (16) with a third insulating film (25) serving as a tunnel film interposed therebetween. Within the semiconductor substrate (11) and in the vicinity of the stepped portion (16), there is formed a depletion control layer (33) which is composed of a heavily doped impurity region and formed to extend from a position located under the floating gate electrode (23) and at a distance from the upper corner of the stepped portion (16) toward the lower corner of the stepped portion (16) and adjoin the end portion of a drain region (32) without reaching a step side region.