A semiconductor memory device includes first conductive layers stacked and second conductive layers stacked in a first direction. The second conductive layers spaced from the first conductive layers in a second direction intersecting the first direction. A first memory pillar is between the first conductive layers and the second conductive layers in the second direction. The first memory pillar extends in the first direction and has a first length in the second direction. A second memory pillar is between the first conductive layers and the second conductive layers in the second direction. The second memory pillar is adjacent to the first memory pillar. The second memory pillar extends in the first direction and has a second length greater than the first length in the second direction.