varma_cs012 had right answer. MIM need extra mask and photo-steps. MOM don't need and the unit capacitance is smaller than MIM usually. As a result, bigger area is needed for MOM.
MIM (metal-insulator-metal) capacitor is a parallel-plate capacitor formed by two planes of metal separated by a very thin (usually high K) dielectric.
MOM (metal-oxide-metal, or VPP - vertical parallel-plate, or VNC - vertical natural capacitor) is an inter-digitated multi-finger capacitor formed by multiple metal layers (optionally connected by vias) in the vertical BEOL (back-end-of-line) stack separated by inter-metal dielectrics.
For deep sub micron (<100nm) with narrow minimum horizontal spacing between metals the interdigitated MOM style caps can be as area efficient as MIM caps but don't need extra process steps.
I'm confused whether MOM cap is fabricated in one metal layer with the interdigitation style or two metal layer with the interdigitation style?
I can't understand with timof's "via connection".
Thank you for your attention
MOM is oxide. Could be grown aluminum oxide, could
be deposited glass.
MIM could be, but does not have to be, oxide. I have
seen nitride on molybdenum for example (a very nice,
robust, good-matching system but who the hell really
wants molybdenum interconnect anymore, or does it?).
Regardless, what your foundry makes is what you get,
and you just get to live with it.
I'm confused whether MOM cap is fabricated in one metal layer with the interdigitation style or two metal layer with the interdigitation style?
I can't understand with timof's "via connection".
Thank you for your attention
Usually MOM capacitors are fabricated using multiple metal layers (to have higher capacitance density, i.e. capacitance per unit area). See attached picture with a schematic drawing.
"MOM" stands for "metal-oxide-metal", but MOM capacitors are using whatever is available in the BEOL (back end of line) stack as a dielectric - for example, in modern technologies, the dielectric is a complicated stack of thin high-K (i.e. SiN) and thick low-K dielectrics.