Embodiments of interconnect structures of a three-dimensional (3D) memory device and method for forming the interconnect structures are disclosed. In an example, a 3D NAND memory device includes a substrate, an alternating layer stack including a staircase structure on the substrate, and a barrier structure extending vertically through the alternating layer stack. The alternating layer stack includes an alternating dielectric stack and an alternating conductor/dielectric stack. The alternating dielectric stack includes dielectric layer pairs enclosed by at least the barrier structure. The alternating conductor/dielectric stack includes conductor/dielectric layer pairs. The memory device further includes a channel structure and a slit structure each extending vertically through the alternating conductor/dielectric stack, an etch stop layer on an end of the channel structure, and first contacts. Each of a conductor layer of the alternating conductor/dielectric stack in the staircase structure, the etch stop layer, and the slit structure is in contact with one of the first contacts.