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Trench-gated power MOSFET with protective diode

  • US 5,998,836 A
  • Filed: 04/30/1997
  • Issued: 12/07/1999
  • Est. Priority Date: 06/02/1995
  • Status: Expired due to Term
First Claim
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1. A trench-gated vertical power MOSFET comprising:

  • a semiconductor chip, said chip comprising a drain region of a first conductivity type;

    a gate positioned in a trench formed in a surface of said semiconductor chip, said trench defining a two-dimensional array of cells, each of said cells being in the shape of a closed figure and being surrounded on all sides by said trench, each cell in a first group of said cells comprising a MOSFET cell and each cell in a second group of said cells comprising a diode cell, each of said MOSFET cells comprising;

    a source region of said first conductivity type and a body region of a second conductivity type adjoining said source region, said body region comprising a channel region adjacent a side of said trench, said channel region being for conducting a current between said source and drain regions when said power MOSFET is turned on;

    each of said diode cells comprising;

    a protective diffusion of said second conductivity type, said protective diffusion forming a junction with said drain region so as to form a diode, said diode being connected in parallel with said channel region in each of said MOSFET cells, said diode cell containing no channel region adjacent a side of said trench; and

    wherein said diode cells are distributed at repetitive intervals in said two-dimensional array, there being a predetermined number of MOSFET cells for every diode cell in said array, said diode cells being positioned in said array so as to limit the strength of an electric field and the formation of hot carriers in the vicinity of said trench throughout said array.

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