A memory device and a method for manufacturing the memory device are provided. The memory device includes a substrate, a plurality of first gate structures, a first dielectric layer, a second dielectric layer, a third dielectric layer and a contact plug. The first gate structures are formed on an array region of the substrate. The first dielectric layer is formed on top surfaces and sidewalls of the first gate structures. The second dielectric layer is formed on the first dielectric layer and in direct contact with the first dielectric layer. The second dielectric layer and the first dielectric layer are made of the same material. The third dielectric layer is formed between the first gate structures and defines a plurality of contact holes exposing the substrate. The contact plug fills the contact holes.