Semiconductor memory device and manufacturing method for same

A method of manufacturing a semiconductor memory device, comprising:

• forming a first conductive layer on a substrate;
• forming a first sacrificial layer on the first conductive layer;
• forming a second conductive layer on the first sacrificial layer;
• removing a portion of the second conductive layer to form a first groove therethrough that reaches the first sacrificial layer;
• forming a second sacrificial layer in the first groove;
• alternately stacking a plurality of second insulating layers and a plurality of third insulating layers on the second conductive layer and the second sacrificial layer;
• removing a portion of the second insulating layers and the third insulating layers to form a second groove that reaches the second sacrificial layer;
• removing the second sacrificial layer and the first sacrificial layer via the second groove to form a cavity on the first conductive layer;
• and
• forming a third conductive layer in the cavity.