Provided is a memory device including a substrate, a plurality of first stack structures, and a plurality of second stack structures. The substrate includes an array region and a periphery region. The first stack structures are disposed on the substrate in the array region. Each first stack structure sequentially includes: a first tunneling dielectric layer, a first floating gate, a first inter-gate dielectric layer, a first control gate, a first metal layer, a first cap layer, and the first stop layer. The second stack structures are disposed on the substrate in the periphery region. Each second stack structure sequentially includes: a second tunneling dielectric layer, a second floating gate, a second inter-gate dielectric layer, a second control gate, a second metal layer, a second cap layer, and the second stop layer. The first stack structures have a pattern density greater than a pattern density of the second stack structures.