A method for forming a 3D memory device is disclosed. A channel structure extending vertically through a dielectric stack including interleaved sacrificial layers and dielectric layers above a substrate is formed. A sacrificial plug above and in contact with the channel structure is formed. A slit opening extending vertically through the dielectric stack is formed. A memory stack including interleaved conductive layers and the dielectric layers is formed by replacing, through the slit opening, the sacrificial layers with the conductive layers. A first contact portion is formed in the slit opening. The sacrificial plug is removed after forming the first contact portion to expose the channel structure. A channel local contact above and in contact with the channel structure, and a second contact portion above the first contact portion in the slit opening are simultaneously formed.