Embodiments of the present disclosure generally relate to an improved method for forming a dielectric film stack used for inter-level dielectric (ILD) layers in a 3D NAND structure. In one embodiment, the method comprises providing a substrate having a gate stack deposited thereon, forming on exposed surfaces of the gate stack a first oxide layer using a first RF power and a first process gas comprising a TEOS gas and a first oxygen-containing gas, and forming over the first oxide layer a second oxide layer using a second RF power and a second process gas comprising a silane gas and a second oxygen-containing gas.