Silicon-rich oxides (SRO) produced by plasma-enhanced chemical vapor deposition (PECVD) are found to possess improved moisture resistance compared with stoichiometric silicon dioxides. The thicknesses of sub-atmospheric chemical vapor deposited (SACVD) ozone-tetraethoxysilane (O-3-TEOS) oxides are shown to be sensitive to the underlying metal layers. The incorporation of a PECVD-SRO underlayer between the metal and SACVD O-3-TEOS oxide eliminates this problem and improves the gap filling. This underlayer, when integrated into the inter-metal dielectric (IMD) structures, also enhances the resistance of poly-Si load resistors and improves the hot carrier reliability of an n-channel metal oxide semiconductor (NMOS) memory device.