Power mosfets and cell topology

Abstract

A MOSFET device formed in a semiconductor chip with a top surface and a bottom surface. The MOSFET device includes a drain region doped with impurities of a first conductivity type, formed near the bottom surface. The MOSFET device further includes a plurality of vertical cells wherein each of the vertical cell includes a vertical pn-junction zone region includes a lower-outer body region, doped with impurities of a second conductivity type, formed on top of the drain region. The pn-junction region further includes a source region, doped with impurities of the first conductivity type, formed on top of the lower-outer body region, the lower-outer body region surrounding the source region and extending to the top surface thus defining a cell area for the cell. The vertical cell further includes a source contact formed on the top surface contacting the source region. The MOSFET further includes a plurality of gates. Each gate is formed on the top surface as a poly layer extending from an area near a boundary of the source region and the lower-outer body region of one of the cells to a neighboring cell, the gate includes a thin insulative bottom layer for insulating from the vertical cell, the gate is provided for applying a voltage thereon for controlling a charge state of a channel underneath each of the gates thus controlling a vertical current from the source contact to the drain region. The MOSFET device further includes a plurality of open stripes whereby a width of the channel is increased and a JFET resistance for each of the vertical cells is decreased.