SEMICONDUCTOR MEMORY DEVICE AND METHOD FOR FABRICATING THE SAME

A semiconductor memory device includes a substrate including a trench and a contact recess, a direct contact placed inside the trench and having a width smaller than a width of the trench, a bit line structure placed on the direct contact and having a width smaller than the width of the trench, a spacer structure placed on side surfaces of the direct contact and the bit line structure, and a buried contact spaced apart from the direct contact and the bit line structure by the spacer structure and filling the contact recess. The spacer structure includes an oxide film placed between the direct contact and the buried contact inside the trench, a seed layer placed on the oxide film inside the trench between the direct contact and the buried contact, and a bulk layer filling the trench on the seed layer and including silicon nitride. The seed layer includes carbon.