A method for manufacturing a semiconductor memory device includes forming a first insulating layer on a conductive layer; forming a second insulating layer on the first insulating layer, the second insulating layer including a first layer and a second layer having nitrogen and hydrogen bonds with higher density than a density thereof in the first layer; forming a third insulating layer on the second insulating layer; forming a semiconductor layer extending through the first insulating layer and the second insulating layer in a direction toward the third insulating layer from the conductive layer; selectively removing the second insulating layer to form a space, the first insulating layer being exposed in the space; forming the fourth insulating layer between the conductive layer and the first insulating layer, the fourth insulating layer being formed by thermally oxidizing the conductive layer through the first insulating layer in the space.