A testing structure was developed to more effectively detect the poly stringer defects in contemporary CMOS ICs. This structure is much more sensitive to poly stringer defects and is closer to the real product layout than the currently widely used structure using an active dummy underneath a poly comb. Many testing structure pieces manufactured in a 0.11 μm copper process line were used to compare the current design with the conventional testing structure. The data shows that the new structure more efficiently detects poly stringers. The results also show that the poly stringers are related to the shallow trench isolation (STI) width. This structure can be used to identify new designs for manufacturing rules for the active space. Thus, this method is very useful for IC foundries to detect poly stringers and to characterize the processing line capability and tune the process recipe to improve product yields. A testing structure was developed to more effectively detect the poly stringer defects and is closer to the real product layout than than the currently widely used structure using an active dummy underneath a poly comb Many testing structure pieces manufactured in a 0.11 μm copper process line were used to compare the current design with the conventional testing structure. The data shows that the new structure be efficient than poly stringers. The results also show that the poly stringers are related to the shallow trench isolation (STI) width. This structure can be used to identify new designs for manufacturing rules for the active space. Thus, this method is very useful for IC foundries to detect poly stringers and to characterize the processing line capability and tune the process recipe to improve product yields.