source electrode 92 in this case the p body region may be connected to the source electrode at various points dimensionally into the page of the figure in one embodiment source electrode 92 may protrude through n source 87 to contact the underlying p body region 86 see fig5 k the trench gate structure of the embodiment of fig4 potentially offers an advantage of a simplified manufacturing process due to the elimination of the t shaped semiconductor regions shown in fig1 also the vertical hvnmos structure of transistor 80 may provide lower on resistance due to the elimination of the jfet structure formed between the p body regions fig5 a 5k illustrate the various processing steps that may be employed to fabricate a vertical high voltage transistor in accordance with the present invention the described fabrication method may be used not only to form the device of fig5 k but also the vertical device structure shown in fig4 fig5 a shows a vertical high voltage transistor after the initial processing step of forming an epitaxial layer 101 of n type semiconductor material on an n substrate 100 to support applied voltages in the range of 200v to 1000v the device structure should have an epitaxial layer that is about 15 um to 120 um thick by way of example the epitaxial layer of the device shown in fig5 is 40 um thick the n substrate 100 is heavily doped to minimize its resistance to current flowing through to the drain electrode which is located on the bottom of the substrate in the completed device substrate 100 may be thinned for example by grinding or etching and metal may be deposited on its bottom surface to further reduce the on resistance of the transistor most often these processing.