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Dynamic random access memory having trench capacitors and vertical transistors

  • US 5,177,576 A
  • Filed: 05/06/1991
  • Issued: 01/05/1993
  • Est. Priority Date: 05/09/1990
  • Status: Expired due to Term
First Claim
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1. A semiconductor memory device including:

  • a semiconductor substrate;

    a plurality of word lines disposed on said semiconductor substrate;

    a plurality of bit lines disposed on said semiconductor substrate and crossing said word lines; and

    a plurality of memory cells disposed on said semiconductor substrate and connected electrically to said word lines and to said bit lines,wherein each of said memory cells includes a switching transistor and a charge storage capacitor which are formed in a trench bored in said semiconductor substrate,wherein said charge storage capacitor is formed by a lower portion in said trench,wherein said switching transistor is formed by an upper portion in said trench, said upper portion being formed immediately above said lower portion in said trench,wherein said lower portion comprises;

    a hollow cylindrical first semiconductor region whose outer periphery is encompassed by a first insulating film,a second insulating film formed at an inner periphery of said hollow cylindrical first semiconductor region, anda second semiconductor region formed inside said inner periphery of said hollow cylindrical first semiconductor region through said second insulating film, a first electrode and a second electrode of said change storage capacitor being formed by said hollow cylindrical first semiconductor region and said second semiconductor region, respectively, and a capacitor insulating film between said first electrode and said second electrode of said charge storage capacitor being formed by said second insulating film, andwherein said upper portion comprises;

    a hollow cylindrical third semiconductor region whose outer periphery is encompassed by a third insulating film,a fourth insulating film formed at an inner periphery of said hollow cylindrical third semiconductor region, anda conductive region formed inside said inner periphery of said hollow cylindrical third semiconductor region through said fourth insulating film, a gate electrode of said switching transistor being formed by said conductive region and connected to a corresponding word line, one of a source region and a drain region of said switching transistor being formed by a top portion of said hollow cylindrical third semiconductor region and connected to a corresponding bit line, the other of said source region and said drain region being formed by a bottom portion of said hollow cylindrical third semiconductor region and connected to said second semiconductor region of said second electrode of said charge storage capacitor,wherein both said bottom portion of said hollow cylindrical third semiconductor region and said second semiconductor region form a common semiconductor region serving as a charge storage node of a memory cell, and wherein said common semiconductor region serving as said charge storage node of said memory cell is electrically isolated by said first insulating film, said second insulating film and said third insulating film from said semiconductor substrate.

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