The effects of back end of line (BEOL) processing with low dielectric constant (low-k) materials on active and field devices' performances have been studied. The study reveals: 1) There is SPICE model uncertainty because Idsat increases as more metal layers are added; 2) Low-k dielectrics can enhance this Idsat increase; and 3) NMOSFETs hot carrier lifetime and PMOSFETs Vt stability are degraded. These effects are attributed to the BEOL-induced hydrogen generation and passivation with gate oxide dangling bonds, which are primarily created in the contact etching process. The modified process involves pure hydrogen alloy after metal-1 formation, which ensures the same device performance at metal-1 and at the final metal layer. In addition, the alloy can reduce the inverse narrow width effect and field isolation leakage currents.