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Method of making a high-density DRAM structure on SOI

  • US 5,466,625 A
  • Filed: 11/22/1994
  • Issued: 11/14/1995
  • Est. Priority Date: 06/17/1992
  • Status: Expired due to Fees
First Claim
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1. A method of forming a pair of integrated circuit, shared gate, cells for dynamic random access memories, comprising in combination:

  • patterning a silicon source layer on a silicon-on oxide wafer comprised of an oxide layer on the upper surface of an underlying support wafer;

    etching a pair of capacitor trenches that extend through said patterned silicon source layer and said oxide layer and into said underlying support wafer;

    conformally depositing a first capacitor plate layer on the wall of each of said pair of said capacitor trenches, said first capacitor plate layer extending to and connected with said silicon source layer;

    forming a capacitor dielectric layer on said polysilicon capacitor plate layer;

    forming an silicon channel layer conformally over said capacitor dielectric layer and overlying a region of said silicon source layer, said silicon channel layer forming a second capacitor plate and a channel layer;

    forming a polysilicon drain layer overlying said silicon channel layer in said region where said silicon channel layer overlays said silicon source layer;

    etching a vertical opening extending through silicon source layer, said silicon channel layer, and said polysilicon drain layer forming a pair of facing vertical wall surfaces in the region where the layers overlay one another with an edge in each layer respectively aligned vertically along said pair of facing vertical wall surfaces, said silicon channel layer extending from one of said facing wall surfaces forming the channel layer and the second capacitor plate layer for one cell of said pair of integrated circuit cells and said silicon channel layer extending from the other of said facing wall surfaces forming the channel layer and the second capacitor plate layer for the other cell of said pair of integrated circuit cells;

    forming a gate dielectric covering said pair of facing vertical wall surfaces; and

    forming a vertical gate in said opening in contact with said gate dielectric.

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