FIG. 1B illustrates a cross-sectional view of the structure of FIG. 1A following source region formation. In accordance with an embodiment of the present invention, a source region 110 is formed on the uppermost, exposed surface of the vertical channel region 106. In one embodiment, as depicted, the uppermost surface of the vertical channel region 106 is below the height of the STI layer 108. As such, at least a lower portion of the source region is confined by the opening(s) 109 and, thus, the aspect ratio of the source region 110 may be trapped. In one embodiment, a second portion of the source region is formed above and expands over a portion of the STI layer 108, as is also depicted in FIG. 1B. Nonetheless, it is to be appreciated that, in one embodiment, epitaxial formation of the source region 110 is selective in that the growth only occurs on/from the vertical channel region 106 and does not initiate on the STI layer 108.