Some embodiments include apparatuses, and methods of operating the apparatuses. Some of the apparatuses include a first group of conductive materials interleaved with a first group of dielectric materials, a first pillar extending through the first group of conductive materials and the first group of dielectric materials, memory cells located along the first pillar, a conductive contact coupled to one of the conductive materials, and a second pillar extending through a second group of conductive materials and a second group of dielectric materials. The second pillar includes a first portion coupled to a conductive region, a second portion, and a third portion, and a fourth portion coupled to the conductive contact. The second portion is located between the first and third portions. The second portion has a doping concentration less than a doping concentration of each of the first and fourth portions.