Disclosed herein are various methods and structures using contacts to create differential stresses on devices in an integrated circuit (IC) chip. An IC chip is disclosed having a p-type field effect transistor (PFET) and an n-type field effect transistor (NFET). One embodiment of this invention includes creating this differential stress by varying the deposition conditions for forming PFET and NFET contacts, for example, the temperature at which the fill materials are deposited, and the rate at which the fill materials are deposited. In another embodiment, the differential stress is created by filling the contacts with differing materials that will impart differential stress due to differing coefficient of thermal expansions. In another embodiment, the differential stress is created by including a silicide layer within the NFET contacts and/or the PFET contacts.