Sub-resolution rod in the transition region

The present disclosure provides a photomask. The photomask includes a first integrated circuit (IC) feature formed on a substrate; and a second IC feature formed on the substrate and configured proximate to the first IC feature. The first and second IC features define a dense pattern having a first pattern density. The second IC feature is further extended from the dense pattern, forming an isolated pattern having a second pattern density less than the first pattern density. A transition region is defined from the dense pattern to the isolated pattern. The photomask further includes a sub-resolution rod (SRR) formed on the substrate, disposed in the transition region, and connected with the first IC feature.