of the present invention in a first level of interconnect structure according to the present invention metal interconnect 60 metal plugs 58 and air gaps 68 are shown embedded in dielectric layer 14 above device layer 10 note that as with fig1 the resulting structure of fig3 shows that that air gaps 68 can extend below the level of the upper surface of device layer 50 and above the upper surface of metal lines 60 thus providing maximum electrical isolation also shown in fig3 is a second level of metal interconnect layer 80 that includes an additional metal level 86 metal plugs 84 and air gaps 88 air gap 88 provides intra level metal isolation and extends to layers 50 52 and 60 a fourth embodiment is now described with reference to fig3 38 this embodiment is a variant of the first embodiment in which an etch stop layer between a line dielectric and a via dielectric is eliminated to further reduce the effective dielectric constant of the inter metal dielectric layer thus in fig3 the second etch stop layer 16 between the via and line dielectric layers 14 and 18 fig2 has been eliminated to further reduce the effective dielectric constant of the inter metal dielectric layer in lieu of two dielectric layers separated by an etch stop layer a single.