A memory device includes a stack and a plurality of memory strings. The stack is disposed on the substrate, and the stack includes a plurality of conductive layers and a plurality of insulating layers alternately stacked. The memory strings pass through the stack along a first direction, wherein a first memory string in the memory strings includes a first conductive pillar and a second conductive pillar, a channel layer, and a memory structure. The first conductive pillar and the second conductive pillar respectively extend along the first direction and are separated from each other. The channel layer is disposed between the first conductive pillar and the second conductive pillar. The memory structure surrounds the second conductive pillar, and the memory structure includes a resistive memory material.