In accordance with the invention, {HEAD ~ a low dielectric constant insulation material} is provided which comprises {TAIL ~ a porous insulation layer}, preferably sandwiched between non porous upper and lower insulation layers 
comprises
In accordance with the invention , { HEAD ~ a low dielectric constant insulation material } is provided which comprises { TAIL ~ a porous insulation layer } , preferably sandwiched between non porous upper and lower insulation layers
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH