A semiconductor memory device includes a semiconductor substrate, bit line structures, storage node contacts, and isolation structures. The bit line structures, the storage node contacts, and the isolation structures are disposed on the semiconductor substrate. Each bit line structure is elongated in a first direction, and the bit line structures are repeatedly disposed in a second direction. Each storage node contact and each isolation structure are disposed between two of the bit line structures adjacent to each other in the second direction. Each storage node contact is disposed between two of the isolation structures disposed adjacent to each other in the first direction. Each isolation structure includes at least one first portion elongated in the first direction and partially disposed between one of the bit line structures and one of the storage node contacts adjacent to the isolation structure in the second direction.