In an example, a three-dimensional (3D) memory device includes a memory stack and a through stair contact (TSC). The memory stack includes interleaved conductive layers and dielectric layers. The memory stack includes stairs in a staircase region. The TSC extends through the memory stack in the staircase region. The TSC includes a first conductor layer and a first spacer circumscribing the first conductor layer. The first conductor layer of the TSC is insulated from the conductive layers of the memory stack by the first spacer.