The a-Si films deposited by the r.f. magnetron sputtering technique were used for fabrication of a-Si(n-type)/c-Si(p-type) structures which were reported to have selective sensitivity in the wavelength range 0.7-1.10 mu m. Spectral dependencies of a-Si/c-Si photosensitivity for the different amorphous Si film thicknesses, substrate temperature, annealing conditions and applied bias voltage were investigated. It was shown that the position of the maximum and its value can be adjusted by the substrate predeposition temperature, post-deposition heat treatment and applied bias voltage. The results show that a-Si(n-type)/c-Si(p-type) structures prepared by the r.f. magnetron sputtering technique can be used in the well-developed Si technology for the IR detector fabrication.