Methods of forming integrated circuit memory devices using masking layers to inhibit overetching of impurity regions and conductive lines

Abstract

Methods of forming integrated circuit memory devices may include steps to form memory cell access transistors therein. These steps may include steps to form a gate line on a semiconductor substrate and then implant dopants of first conductivity type into the semiconductor substrate to define a self-aligned impurity region therein. A spacer layer of a first material is then formed on a sidewall and upper surface of the gate line. An interlayer insulating layer of a second material is then formed on the spacer layer. A series of selective etching steps are then performed using different etchants. For example, a step is performed to selectively etch the interlayer insulating layer to define a contact hole therein, using the spacer layer as an etching mask to protect the gate line from etching damage. A selective etching step is then performed to convert the spacer layer into a sidewall spacer on the sidewall of the gate line. This etching step is performed using the interlayer insulating layer as an etching mask. A conductive plug (e.g., bit line plug) is then formed in the contact hole. This conductive plug forms an ohmic contact with the impurity region.