Electron-masking processes require highly-sensitive resins, either negative or positive, providing a good definition. In this paper the authors go into the preparation and quality of these resins. The first part relates to the mechanistic action of electrons on polymers, the synthesis and features of some polysiloxane resins. The latter are highly sensitive to electrons, the charge density required for cross-linking being 5. 10** minus **6C. cm** minus **2. The second part relates to improving the characteristic properties of a positive resin, viz. , polymethyl methacrylate. The extent of the molecularweight spread of this polymer on its electron-sensitivity is clearly shown. The last part is devoted to investigating silica films derived through thermal treatment of polysiloxane resins and the relevant applications, such as etching of chromium-in-contact masks, insulation of dual metal-interconnection films, making of light guides for built-in optical systems. 21.