Patent ID: 8193059
Filing Date: 2012-06-05
Classification: H01L

Abstract:
1. A fabrication method for a bit line structure, the method comprising: preparing a substrate; forming a trench in the substrate, the trench having a bottom and sidewall portions extending from the bottom along the length of the trench; forming a first trench insulating layer at a bottom of the trench and at least portions of the sidewall of the trench; forming a first trench filling layer at a surface of the trench insulating layer in a lower section of the trench, the first trench filling layer substantially filling a lower section of the trench and thereby forming a single continuous planar surface at the top of the trench filling layer; forming a second trench insulating layer on the surface at the top of the first trench filling layer; forming a second electrically conductive trench filling layer as a buried bit line on the top side of the surface of the second trench insulating layer, which fills an upper section of the trench up to a surface of the substrate; forming a word line stack at the substrate surface; forming first and second doping regions in the substrate and on opposite sides of the trench, portions of the first and second doping regions being directly adjacent to the first trench insulating layer; forming a first electrically conductive connection layer that electrically connects the first doping region to the second trench filling layer, and is directly adjacent to the first doping region, the first trench insulating layer, and the second electrically conductive trench filling layer; forming a surface dielectric at the substrate surface; forming a second electrically conductive connection layer in the surface dielectric; forming a surface bit line at a surface of the surface dielectric such that the surface bit line contacts the second connection layer; and wherein the buried bit line is formed at a top surface of the second trench insulating layer, the second trench insulating layer isolates the buried bit line from the first trench filing layer.