Three-dimensional memory device with shielding layer and forming method thereof

Embodiments of a three-dimensional (3D) memory device having a shield layer and methods for forming the 3D memory device are disclosed. In an example, a 3D memory device includes: the memory device includes a substrate, a peripheral device disposed on the substrate, a semiconductor layer disposed over the peripheral device, a plurality of memory strings each extending vertically on the semiconductor layer, and a shield layer disposed between the peripheral device and the semiconductor layer. The shielding layer includes a conductive region configured to receive a ground voltage during an operation of the 3D memory device.