A memory device includes a memory cell, a writing transistor, and a reading transistor. The memory cell includes a semiconductor substrate, a tunneling layer, a storage layer, a first electrode, a second electrode, and a third electrode. The tunneling layer is over the semiconductor substrate. The storage layer is on the tunneling layer. The first electrode is on the storage layer. The second electrode is on the tunneling layer. The storage layer has a sidewall facing the second electrode. The third electrode is spaced apart from the second electrode. The writing transistor is electrically connected to the first electrode of the memory cell. The reading transistor is electrically connected to the second electrode of the memory cell.