Memory devices and methods for manufacturing are described herein. A memory device described herein includes a plurality of memory cells. Memory cells in the plurality of memory cells comprise respective bipolar junction transistors and memory elements. The bipolar junction transistors are arranged in a common collector configuration and include an emitter comprising doped polysilicon having a first conductivity type, the emitter contacting a corresponding word line in a plurality of word lines to define a pn junction. The bipolar junction transistors include a portion of the corresponding word line underlying the emitter acting as a base, and a collector comprising a portion of the single-crystalline substrate underlying the base.