In some embodiments, the present disclosure relates to a semiconductor device including a semiconductor region over a bulk oxide, which is over a semiconductor substrate. Above the bulk oxide is a lower source region that is laterally spaced from a lower drain region by a lower portion of the semiconductor region. An upper source region is laterally spaced from an upper drain region by an upper portion of the semiconductor region and is vertically spaced from the lower source region and the lower drain region. The upper source region is coupled to the lower source region, and the upper drain region is coupled to the lower drain region. A gate electrode, coupled to the semiconductor substrate and over a gate oxide, is above the upper portion of the semiconductor region. The lower and upper portions of the semiconductor region respectively include a first channel region and a second channel region.