We present the combination of alternating phase-shifting masks and rule-based optical proximity correction (OPC) for the patterning of 0.13 mu m polysilicon gate Lines. Using the optimal process condition, a process window with 1.2 mu m of depth of focus (DOF) and 15% exposure latitude is obtained for 0.13 mu m isolated lines in resist. In addition, with the application of rule-based OPC, the common DOF for 0.13 mu m lines of various line-to-space ratios can be improved from 0 to 0.6 mu m.