A method is provided for manufacturing a memory device. A plurality of layers of a first semiconductor material is formed, and a plurality of holes is formed through the layers. An etch process is applied to the layers through the holes, to form pull-back regions in the layers adjacent and surrounding the holes. A film of second semiconductor material is deposited over the holes and into the pull-back regions. Portions of the film are removed from the holes while leaving elements of the second semiconductor material in the pull-back regions in contact with the first semiconductor material. The holes are filled with insulating material. Layers in the plurality of layers have respective first doping concentration profiles, and the elements of the second semiconductor material in the pull-back regions have second doping concentration profiles. The second doping concentration profiles establish a higher conductivity in the elements of second semiconductor material.