The present invention relates to a substrate comprising a build-up and a solder resist layer disposed on the build-up. The solder resist layer has an upper surface facing away from the build-up. The solder resist layer has a plurality of grooves on its upper surface. The grooves of the solder resist layer can better eliminate or relieve the stress accumulated on large solder resist area induced by heat and/or material coefficient of thermal expansion mismatch of the substrate and thus can prevent and diminish warpage of the substrate or package.