A vertical insulated gate field effect transistor having a first conductivity layer, a second conductivity layer thereon, a third first conductivity layer thereon, a groove extending from the surface of the third layer through the second layer into the first layer, a layer of insulation and gate material...http://www.google.es/patents/US4296429?utm_source=gb-gplus-sharePatente US4296429 - VMOS Transistor and method of fabrication
