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High frequency switching MOSFETs with low output capacitance using a depletable P-shield

  • US 8,946,816 B2
  • Filed: 05/05/2014
  • Issued: 02/03/2015
  • Est. Priority Date: 12/21/2012
  • Status: Active Grant
First Claim
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1. A MOSFET device, comprising:

  • a semiconductor substrate of a first conductivity type wherein the substrate includes a lightly doped epitaxial region in a top portion of the substrate;

    a body region of a second conductivity type formed in a top portion of the semiconductor substrate, wherein the second conductivity type is opposite the first conductivity type;

    a plurality of active device structures formed from the semiconductor substrate and body region, wherein each active device structure comprises a gate electrode formed in a trench and insulated with a gate oxide, wherein an upper portion of the gate oxide is a thickness T1 and a bottom portion of the gate oxide is a thickness T2, wherein T2 is greater than T1;

    a depletable shield of the second conductivity type formed in the semiconductor substrate at a depth at least partially below a bottom surface of one or more trenches, wherein the depletable shield is electrically connected to the body region;

    an insulative gate cap formed over each gate electrode, wherein an insulating spacer is formed on the sidewalls of the gate cap and a conductive or semiconductor spacer is formed on the exposed side walls of the insulating spacer, an insulative layer over a top surface of the body region;

    a conductive source metal layer formed over the insulative layer;

    one or more electrical connections that connect the source metal layer with one or more source regions, wherein the one or more electrical connections are spaced apart from the gate cap by the insulative spacers.

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