Methods and apparatuses for modifying a work function of transistors included in an integrated circuit are disclosed. A tester unit may be configured to test an integrated circuit that includes a plurality of circuit paths. The tester unit may be further configured to analyze the results from testing the integrated circuit and, based on the analysis, identify a circuit path that fails to meet a desired performance goal. A work function of a transistor included in the identified circuit path may be modified by the tester unit using an energy source external to the integrated circuit.