Embodiments of a three-dimensional (3D) memory device are provided. The 3D memory device includes a substrate, a memory stack with interleaved conductive layers and dielectric layers over the substrate, an array of channel structures each extending vertically through the memory stack, and a plurality of contact hole structures each extending vertically through the memory stack and electrically connected to a common source of one or more of the channel structures. At least one of the plurality of contact hole structures is surrounded by a plurality of the channel structures of nominally equal lateral distances to the respective contact hole structure.