Resistor elements and methods of forming the resistor elements generally include increasing resistivity by diffusing nitrogen ions from an underlying dielectric layer into a metal resistor layer defining the resistor elements. One or more embodiments include a first resistor element and at least one additional resistor element disposed on a first dielectric material and at least one additional dielectric material, respectively, of a dielectric layer. The first dielectric material is different from the at least one additional dielectric material, and the first resistor element has a different resistivity than the at least one additional resistor element.