Techniques for fabricating a memory device which has reduced neighboring word line interference, and a corresponding memory device. The memory device comprises a stack of alternating conductive and dielectric layers, where the conductive layers form word lines or control gates of memory cells. In one aspect, rounding off of the control gate layers due to inadvertent oxidation during fabrication is avoided. An amorphous silicon layer is deposited along the sidewall of the memory holes, adjacent to the control gate layers. Si3N4 is deposited along the amorphous silicon layer and oxidized in the memory hole to form SiO2. The amorphous silicon layer acts as an oxidation barrier for the sacrificial material of the control gate layers. The amorphous silicon layer is subsequently oxidized to also form SiO2. The two SiO2 layers together form a blocking oxide layer.