Method for forming a finely patterned photoresist layer

In a method for the formation of a patterned photoresist layer on the surface of a substrate with intervention of an anti-reflection film by a photolithographic patterning process comprising the steps of forming an anti-reflection coating film containing a resinous ingredient, a highly light-absorbing compound and a thermally crosslinkable compound on the substrate surface, forming a photoresist layer on the anti-reflection coating film, patternwise exposing the photoresist layer to a light and subjecting the patternwise exposed photoresist layer to a development treatment, the improvement which comprises controlling the refractive index and the light-absorption coefficient of the anti-reflection coating film in such a way that, in a graph prepared by plotting the thickness of the anti-reflection coating film taken as the abscissa values and the reflectivity of the light for patterning exposure at the interface between the anti-reflection coating film and the photoresist layer thereon taken as the ordinate values, the range of the variation in the film thickness corresponding to an increment of 0.01 in the reflectivity in the vicinity of the minimum point on the thickness vs. reflectivity curve does not exceed ±0.01 μm.