The invention relates to lithography for etching very high-density patterns on a substrate, for example for producing microelectronic integrated circuits. A high-density pattern is etched using a combination of a plurality of less-dense partial patterns; a sacrificial film is formed on a substrate (10) and the sacrificial film is etched in a first partial pattern; spacers are formed on the edges of the elements of the sacrificial film thus etched, the spacers defining a second partial pattern; and then the sacrificial film is removed so as to leave in place only the spacers (16). Next, a film (22) sensitive to an electron beam is deposited between the spacers with a thickness that is smaller than or equal to the height of the spacers; and this sensitive film is exposed, by means of an electron beam, in a third partial pattern such that there remains on the substrate a final pattern of regions containing no spacers and no sensitive film, this pattern resulting from the combination of the second and third partial patterns and having a higher density than each of the partial patterns.