Three-dimensional memory device and manufacturing method thereof

The invention discloses a three-dimensional memory device and a manufacturing method thereof, and the device comprises a substrate which comprises a first region and a second region; a liner layer disposed between the substrate and the memory stack structure; comprising a plurality of conductive layers and dielectric layers which are alternately stacked, the memory stack structure is arranged on the substrate and extends from the first region to the second region, and the memory stack structure on the second region comprises a step structure, wherein steps of the step structure respectively comprise one conductive layer and one dielectric layer, and the side wall of the conductive layer is recessed from the side wall of the dielectric layer to expose a part of the bottom surface of the dielectric layer. The side wall of the conductive layer is recessed from the side wall of the dielectric layer, so that the problem of short circuit between the conductive layer and a subsequently manufactured word line contact