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Spacer flash cell device with vertically oriented floating gate

  • US 5,479,368 A
  • Filed: 09/30/1993
  • Issued: 12/26/1995
  • Est. Priority Date: 09/30/1993
  • Status: Expired due to Fees
First Claim
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1. A nonvolatile memory cell comprising:

  • a. a planar substrate of a semiconductor material having an upper surface and further having a conductive source region and a conductive drain region formed in the upper surface having a channel region therebetween;

    b. a floating gate that is coupled to the substrate, wherein the floating gate is formed of a conductive material that is surrounded by an electrically insulating material and further wherein the floating gate has a cross section which is longer along one axis than it is along its other axis, the floating gate having at least one surface parallel to the longer axis that is substantially perpendicular to the substrate, the floating gate having a sharp tip at an end of the surface furthest from the substrate wherein the floating gate is positioned over and electrically controls only a portion of the channel adjacent the drain; and

    c. a control gate, coupled to the substrate so that the floating gate is between the control gate and the substrate, wherein the control gate is spaced apart from the floating gate by the insulating material such that the control gate only overlaps a portion of the floating gate along the at least one surface parallel to the longer axis that is substantially perpendicular to the substrate furthest from the substrate and only comes into close proximity with the floating gate in this region of overlap wherein the control gate is positioned over the channel and electrically controls only that portion of the channel not controlled by the floating gate, such that the channel is split into two portions wherein a first portion of the channel is controlled by the floating gate and a second portion of the channel is controlled by the control gate and further wherein the floating gate is programmed by hot electron injection from a weakly conducting second portion.

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