Resistor structure and method for forming the same

A method for forming a metal resistor structure, comprising:

• providing a substrate having a first region and a second region, wherein the substrate includes a first metallic interconnection structure and a dielectric layer enclosing the metallic interconnection structure, the metallic interconnection structure includes a first metallic plug disposed in the first region and a second metallic plug disposed in the second region, wherein top surfaces of the first metallic plug, the second metallic plug and the dielectric layer are flush with each other;
• forming a first metallic layer on the top surfaces of the first metallic plug, the second metallic plug and the dielectric layer which are flush with each other;
• forming an insulating material layer on the first metallic layer;
• patterning the insulating material layer to form a first insulating layer above the first region and a second insulating layer above the second region, wherein the first insulating layer and the second insulating layer are isolated from each other, such that the first metallic layer is partially exposed;
• forming a second metallic layer overlaying exposed part of the first metallic layer, the first insulating layer, and the second insulating layer;
• forming a patterned mask layer on the second metallic layer, wherein the patterned mask layer overlays a first portion of the second metallic layer disposed on the first insulating layer, and exposes a second portion of the second metallic layer disposed on the second insulating layer;
• and
• etching, by using the patterned mask layer as a mask, until the substrate is exposed,
• wherein the first portion of the second metallic layer covered by the patterned mask layer, the first insulating layer under the first portion of the second metallic layer, and a first portion of the first metallic layer covered by the first insulating layer, are remained after the etching and thereby constituting a capacitor on the first metallic plug,
• wherein the second portion of the second metallic layer exposed by the patterned mask layer are removed by the etching, and the etching further removes the exposed part of the first metallic layer which is disposed on the second region, thereby a second portion of the first metallic layer which is disposed on the second region and is covered by the second insulating layer constitutes a metallic resistor on the second metallic plug.