A pattern is formed by applying an undercoat layer comprising a naphthol-dicyclopentadiene copolycondensate on a processable substrate as an antireflective film, applying a photoresist layer over the undercoat layer, exposing the photoresist layer to radiation, developing the resist with a developer to form a resist pattern, and dry etching the undercoat layer and the substrate through the photoresist layer as a mask. The undercoat layer has an optimum refractive index to provide a satisfactory antireflection effect at a film thickness of 200 nm or greater as well as high etching resistance. The shape of resist after patterning remains satisfactory.