A known method of forming organic semiconductor devices employs the deposition of a conductive polymer onto a substrate to form electrodes or conductive tracks and then to apply an electrical material such as an organic semiconductor on top of these tracks. Although the conductive polymer serves as a highly efficient injector of electrons into the semiconductor, it is not a good conductor. This introduces undesirable inefficient in the supply of current to and from the semiconductor. Worse still the conductivity may deteriorate with time. A solution to this problem has been found by printing the polymer (7) onto a conductive layer (6) carried on a substrate (5). The printed polymer (7) is then used as a resist during a process in which parts of the conductive polymer not protected by the polymer are removed. The resulting device benefits from the good electron injection qualities of the conductive polymer (7) and efficient conduction by virtue of the underlying conductive layer (6).