Provided is a memory device including a substrate, isolation structures, conductive pillars, and bit-line structures. The substrate includes active areas. The active areas are arranged as a first array. The isolation structures are located in the substrate and extending along a Y direction. Each of the isolation structures is arranged between the active areas in adjacent two columns. The conductive pillars are located on the substrate and arranged as a second array. The conductive pillars in adjacent two rows are in contact with the active areas arranged as the same column, to form a first contact region and a second contact region. The bit-line structures are arranged on the substrate in parallel along a X direction. Each of the bit-line structures is in contact with the active areas arranged as the same column, to form a third contact region between the first and second regions.