Electron beam lithography is a highly flexible method that can be used to fabricate diffractive optical elements. However the long exposure time required is the most serious point that needs addressing, and this is derived from the lack of sensitivity of the electron beam resist. We have investigated the physical properties of polydimethylsiloxane and poly(dimethylsiloxane-co-methylvinyIsiloxane) for electron beam lithography. The results show that these polysiloxanes exhibit much higher sensitivities than the conventional substances, of 1. 5 and 0.9 muC/cm(2) respectively, and that they have a T value of 1. 3. Using these polysiloxanes, we succeeded in fabricating a four-level phase computer-generated hologram.