why is extra layer used in mim capacitor?

[bhagyasree]

hi,
can any one tell me why fuse material/CTM layer is used in mim capacitors..
And why the capacitor is directly not formed between any two metal layers? why is it formed between one metal and
an extra layer?


Thanks

 

[erikl]

why is it formed between one metal and an extra layer?

in order to use a thinner dielectric medium, so achieving a larger capacitance per area ratio.