IPD seems to imply a postprocessing after the "normal"
top metal layer, and may be done at a different line
than the transistors & interconnect.
There are passive devices (MOS or MIM caps, resistors,
etc.) that -are- integrated during the main flow, of
course. The distinction for IPD is that it happens as
an add-on, at least the flavors I've seen. They may
be higher-Q than a MOSCAP or an inductor with mucho
substrate coupling, this seems to be the primary value-
add.