PURPOSE: To obtain patterns of a rectangular shape in lithography using far UV light by consisting the above resin of the polycondensate of 2-diazomalonic acid and bisphenol.

CONSTITUTION: This photosensitive resin is constituted of the polycondensate of the 2-diazomalonic acid and the bisphenol and, therefore, the reaction that the 2-diazo-1, 3-dicarbonyl structural part changes to β ketocarboxylic acid takes place in the part of this resin irradiated with the far UV light. The part of the photosensitive resin irradiated with the UV rays is, therefore, soluble in an alkaline developer and the light absorbing characteristic of 250mm wave length decreases. The bisphenol has the structure similar to the structure of p-substd. phenol is much smaller in the absorption of the far UV light than cresol novolak resin, etc. The exposing light arrives sufficiently at the bottom of the film in the part of the photosensitive resin irradiated with the far UV light and, therefore, the resist pattern having the shape approximate to the rectangular shape is formed.