High power MOSFET with low on-resistance and high breakdown voltage

Claim 1

A three-terminal power metal oxide silicon field effect transistor device comprising: a wafer of semiconductor material having first and second opposing semiconductor surfaces; said wafer of semiconductor material having a relatively lightly doped major body portion for receiving junctions and being doped with impurities of one conductivity type; at least first and second spaced base regions of the opposite conductivity type to said one conductivity type formed in said wafer and extending from said first semiconductor surface to a depth beneath said first semiconductor surface; the space between said at least first and second base regions defining a common conduction region of one conductivity type at a given first semiconductor surface location; first and second source regions of said one conductivity type formed in each pair of said at least first and second base regions respectively at first and second first surface locations and extending from said first and second first surface locations to a depth less than said depth of said base regions; said first and second source regions being laterally spaced along said first semiconductor surface from the facing respective edges of said common conduction region thereby to define first and second channel regions along said first semiconductor surface between each pair of said first and second source regions, respectively and said common conduction region; source electrode means connected to said source regions and comprising a first terminal; gate insulation layer means on said first surface, disposed at least on said first and second channel regions; gate electrode means on said gate insulation layer means, overlying said first and second channel regions and comprising a second terminal; a drain conductive region remote from said common region and separated therefrom by said relatively lightly doped major body portion; a drain electrode coupled to said drain conductive region and comprising a third terminal; each of said at least first and second spaced base regions of said opposite conductivity type having respective profiles which include relatively shallow depth regions extending from said common region and underlying their said respective first and second source regions, and respective relatively deep, relatively large radius regions extending from said shallow depth regions which are laterally spaced from beneath said respective source regions on the side of said source regions which is away from said common region.