A photomask and method for fabricating an integrated circuit is provided. A design layout is provided, wherein the design layout has a plurality of main features. A plurality of assistant features are added in an assistant region of the design layout to form a first layout, wherein the assistant region has no main feature and a width of the assistant region is larger than five times of a width of the main feature. A plurality of optical proximity correction (OPC) features are added on the first layout to form a second layout. And a photomask is formed according to the second layout.