Method for fabricating a shielded multilevel integrated circuit capacitor

A method for fabricating a capacitor structure on a surface of a semiconductor substrate having a first conductivity type, comprising the steps of:

• a) diffusing a material of a second conductivity type within said substrate to form a diffusion well that is an electrical shield to prevent noise and unwanted external signals from coupling to said capacitor structure;
• b) coupling the diffusion well to a quiet voltage source isolated from said noise and unwanted external signals with a first plurality of contacting means;
• forming over said surface of said diffusion well a first insulating layer;
• forming over said first insulating layer a first conducting material to form a first capacitor plate within a first set of boundaries that define said diffusion well;
• forming over said first insulating layer and said first capacitor plate a second insulating layer;
• forming over said second insulating layer a second conducting material to form a second capacitor plate within a second set of boundaries that define said first capacitor plate;
• forming over said second insulating layer and said second capacitor plate a third insulating layer;
• forming over said third insulating layer a third conducting material to form a third capacitor plate having boundaries equal to those of the first capacitor plate;
• i) forming a second plurality of contacting means to couple said first capacitor plate to said third capacitor plate;
• j) connecting said first capacitor plate and said third capacitor plate to external circuitry;
• and
• k) connecting said second capacitor plate to external circuitry.