A semiconductor memory device and a method for accessing the same are disclosed. The semiconductor memory device includes an oxide heterojunction transistor which includes: an oxide substrate; an oxide film on the oxide substrate, wherein an interfacial layer between the oxide substrate and the oxide film behaves like two-dimensional electron gas; a source electrode and a drain electrode being located on the oxide film and electrically connected with the interfacial layer; a front gate on the oxide film; and a back gate on a lower surface of the oxide substrate, wherein the source electrode and the drain electrode of the oxide heterojunction transistor are respectively connected with a first word line and a first bit line for reading operation, and wherein the front gate and the back gate are respectively connected with a second word line and a second bit line for writing operation.