A semiconductor memory device, which may include a substrate, a lower conductive line on the substrate, an isolation insulating layer on the lower conductive line and including a channel trench, a channel structure inside the channel trench and including a first oxide semiconductor material, an interfacial conductive pattern between the lower conductive line and a lower surface of the channel structure, a gate dielectric layer that covers the channel structure within the channel trench, an upper conductive line on the gate dielectric layer within the channel trench, a conductive contact pattern on the channel structure, an interfacial oxide semiconductor pattern between the channel structure and the conductive contact pattern and including a second oxide semiconductor material, and a capacitor structure including a lower electrode connected to the conductive contact pattern.