Embodiments of 3D memory devices and methods for forming the same are disclosed. In an example, a 3D memory device includes a substrate, a memory stack including interleaved conductive layers and dielectric layers above the substrate, a structure extending vertically through the memory stack, a first dielectric layer on the memory stack, an etch stop layer on the first dielectric layer, a second dielectric layer on the etch stop layer, a first contact through the etch stop layer and the first dielectric layer and in contact with an upper end of the structure, and a second contact through the second dielectric layer and in contact with at least an upper end of the first contact.