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MOS device for long-term learning

  • US 4,953,928 A
  • Filed: 06/09/1989
  • Issued: 09/04/1990
  • Est. Priority Date: 06/09/1989
  • Status: Expired due to Term
First Claim
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1. A semiconductor structure for long term learning including:

  • a p-type region in a semiconductor substrate,a first n-type region disposed in said p-type region,a floating gate disposed above said p-type region, said floating gate at least partially overlapping one edge of said first n-type region and separated from the surface of said substrate by a gate oxide under a portion of said floating gate including at least where it partially overlaps the edge of said first n-type region,means for applying a first positive potential to said first n-type region with respect to said p-type region to reverse bias said first n-type region, said first positive potential having a magnitude of greater than about 3.2 volts relative to said p-type region, but less than the voltage required to induce avalanche breakdown in the junction between said first n-type region and said p-type region,means for capacitively coupling a second positive potential to said floating gate, said second positive potential having a magnitude of greater than about 3.2 volts relative to said p-type region,a second n-type region in contact with said p-type region,means for applying a negative potential to said second n-type region with respect to said p-type region to forward bias said second n-type region, and to thereby inject minority electrons into said p-type region,an insulating layer over said floating gate,a conductive region disposed over said insulating layer and capacitively coupled to said floating gate,means for selectively applying a third positive potential to said conductive region with respect to said floating gate,whereby said first and second positive potentials act to accelerate said minority electrons to an energy sufficient to surmount the barrier energy of said gate oxide and thereby inject said minority electrons onto said floating gate and whereby said third positive potential causes electrons to tunnel from said floating gate to said conductive region.

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