Disclosed are methods for the formation of silicon nitride (SiN) on only the horizontal surfaces of structures such as 3D NAND staircase. This allows for thicker landing pads for subsequently formed vias. In some embodiments, the methods involve deposition of a SiN layer over a staircase followed by a treatment to selectively densify the SiN layer on the horizontal surfaces with respect to the sidewall surfaces. A wet etch is then performed to remove SiN from the sidewall surfaces. The selective treatment results in significantly different wet etch rates (WERs) between the horizontal surfaces and the sidewalls.