In the preferred embodiment, a thick regular-k dielectric is formed on a
substrate. A tungsten plug is formed in the thick regular-k dielectric.
The thick regular-k dielectric is recessed and a thin low-k dielectric is
formed on the thick regular-k dielectric. The thin low-k dielectric acts
as a glue layer and as an etch stop layer. A thick low-k dielectric is
formed on the thin low-k material. Optionally, an opening is formed
through the thick low-k dielectric to expose the tungsten plug. The
opening is then filled with copper or copper alloys.