Disclosed is a chip structure that includes heater. The heater includes a heating element with a first end and a second end and, between the first and second ends, different portions with different cross-sectional areas. The heating element further includes first and second terminals at the first and second ends, respectively. Current flowing through the heating element between the first and second terminals causes the heating element to generate heat. However, due to the different cross-sectional areas of the different portions, the current densities through those different portions are different and, thus, the different portions of the heating element generate different amounts of heat per unit length. The heating element can be designed and placed on-chip to facilitate local thermal tuning of different regions of a device or of different devices without requiring multiple different heating elements within a relatively small chip area. Also disclosed is an associated method.