Semiconductor device and method for fabricating the same

Abstract

The nonvolatile semiconductor memory device of the 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 and second surface regions; 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 capacitively coupled to the floating gate via a second insulating film. The first surface region is an upper surface of an epitaxially grown layer formed on the second surface region. The drain region includes: a low-concentration impurity layer formed in the second surface region and having one end extending toward the step side region; and a high-concentration impurity layer connected to the low-concentration impurity layer and formed in a region distant from the channel region. An impurity concentration of the low-concentration impurity layer is lower than that of the high-concentration impurity layer. The floating gate covers the step side region and at least a part of the low-concentration impurity layer via the first insulating film.