Provided is a memory device including a substrate, a stack structure, a plurality of pads and an additional dielectric layer. The substrate has an array region and a staircase region. The stack structure is disposed on the substrate. The stack structure includes a plurality of dielectric layers and a plurality of conductive layers stacked alternately. The pads are disposed on the substrate in the staircase region. The pads are respectively connected to the conductive layers, so as to form a staircase structure. The additional dielectric layer is disposed on the stack structure to contact a topmost conductive layer of the conductive layers. A topmost pad of the pads includes a landing portion to contact a plug and an extension portion. The landing portion is laterally adjacent to the additional dielectric layer, and the extension portion extends over a top surface of the additional dielectric layer.