The present disclosure relates to a vertical transistor device having rectangular vertical channel bars extending between a source region and a drain region, and an associated method of formation. In some embodiments, the vertical transistor device has a source region disposed over a semiconductor substrate. A channel region with one or more vertical channel bars is disposed over the source region. The one or more vertical channel bars have a bottom surface abutting the source region that has a rectangular shape (i.e., a shape with four sides, with adjacent sides of different length, and four right angles). A gate region is located over the source region at a position abutting the vertical channel bars, and a drain region is disposed over the gate region and the vertical channel bars. The rectangular shape of the vertical channel bars provides for a vertical device having good performance and cell area density.