The present disclosure relates to a semiconductor memory device including a substrate, a plurality of buried word lines, a plurality of bit lines, and a plurality isolation fins. The substrate includes a plurality of active areas and a shallow trench isolation. The buried word lines are disposed in the substrate. The bit lines are disposed on the substrate. The isolation fins are disposed on the substrate, over each of the buried word lines respectively, wherein a portion of the isolation fins is disposed under the bit lines and overlapped with the bit lines.