A memory device includes an insulation layer, a memory cell region and an alignment mark region are defined on the insulation layer, an interconnection structure disposed in the insulation layer, a dielectric layer disposed on the insulation layer and the interconnection structure, the dielectric layer is disposed within the memory cell region and the alignment mark region, a conductive via plug disposed on the interconnection structure within the memory cell region, the conductive via plug has a concave top surface, an alignment mark trench penetrating the dielectric layer within the alignment mark region, a bottom electrode disposed on the conductive via plug within the memory cell region and disposed in the alignment mark trench within the alignment mark region, and a magnetic tunnel junction (MTJ) structure disposed on the bottom electrode within the memory cell region and disposed in the alignment mark trench within the alignment mark region.