Process for manufacture of high power MOSFET with laterally distributed high carrier density beneath the gate oxide

  • US 4,593,302 A
  • Filed: 08/18/1980
  • Issued: 06/03/1986
  • Est. Priority Date: 08/18/1980
  • Status: Expired due to Term
First Claim
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1. A high current MOSFET having low forward resistance comprising a semiconductor chip having first and second parallel surfaces;

  • said chip having a body portion which is relatively lightly doped with impurities of a first conductivity type;

    said body portion extending from said first surface for at least a portion of the thickness of said chip;

    a plurality of local regions of a second conductivity type distributed over and extending into said first surface of said chip;

    a plurality of source regions of said first conductivity type extending into respective ones of said plurality of local regions and having a depth less than the depth of their said respective local region and an outer periphery which is interior of and spaced by a fixed distance from the periphery of said local region at said first surface, thereby to define short conduction channels capable of inversion;

    each of said plurality of local regions being spaced from one another at said first surface by a symmetric mesh of said body portion;

    a mesh-shaped gate insulation layer extending over said mesh between said local regions and overlapping said short conductive channels surrounding said local regions;

    a mesh-shaped gate electrode disposed atop said gate insulation layer;

    a vertical conductive region of said first conductivity type extending from beneath said gate insulation layer and between adjacent local regions and toward said second surface;

    a common source electrode connected to each of said source regions and to each of said local regions;

    said common source electrode extending over said first surface; and

    a drain electrode connected to said second surface;

    said vertical conductive region having a higher doping concentration than that of said body portion for a depth below said first surface which is less than the depth of said local regions;

    said doping concentration in said vertical conductive region having a constant value laterally across said first surface beneath said insulation layer.

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