A method for forming upon a microelectronics layer upon a substrate employed within a microelectronics fabrication a silicon oxide dielectric layer with enhanced density and reduced mobile species, ionic concentration and ionic mobility. There is provided a substrate employed within a microelectronics fabrication. There is formed upon the substrate a blanket undoped silicon oxide glass dielectric layer employing ozone assisted near atmospheric pressure thermal chemical vapor deposition (APCVD) from tetra-ethyl-ortho-silicate (TEOS) vapor, wherein a high flow rate ratio of ozone gas to TEOS vapor affords enhanced density and reduced mobile species, ionic concentration and ionic mobility in the blanket silicon oxide glass dielectric layer. There is then formed a blanket boron-phosphorus doped silicon containing glass dielectric layer over the substrate employing ozone assisted near atmospheric pressure thermal chemical vapor deposition (APCVD) to complete the dielectric layer. The blanket undoped silicon oxide glass dielectric layer serves as a barrier to diffusion of mobile species from the doped silicon containing glass dielectric layer or other dielectric layers to attenuate hot carrier injection effects, which reduces degradation of device reliability.