Nowadays the requirements to the reliability and functionality of modern radio equipment increase. An integral part of any radio-electronic equipment is a semiconductor chip which contains elements based on thin dielectric films. In the process of film deposition, during vapor-oil pumping out, carbon-containing compounds, influencing substantially the electric properties of the produced films, are obligatory present in the working chamber. Investigations of SiO2 + C films demonstrated a significant change in the electric properties of the dielectric attendant to changes in the carbon concentration in the film [1]. We believe that carbon changes the microrelief and porosity of the prepared films; however, the mechanism of carbon influence remains unknown. Our experiments were carried out with the SiO2 + C films 250 nm thick. The dielectric films were prepared by magnetron sputtering of the compound target consisting of a silicon plate with built-in carbon wheels. The amount of sputtered carbon was determined by the area SC occupied by graphite wheels on the silicon target. The concentration of carbon incorporated into SiO2 was changed by changing the number of graphite wheels. The step of changing was a single disk and made 6%. The microrelief was studied with a scanning electron microscope. The electron-microscopic studies demonstrated a significant change of the relief of film surfaces with increase in the carbon concentration in the SiO2 film in the process of sputtering. Figure 1 clearly shows porousity of SiO2 film structure and even the formation of through pores with increasing percentage of carbon on the compound target. With increase in the carbon concentration, not only the number of through pores in the film increases, but also the surface microrelief changes, leading to the porous film structure. The given result was repeated and was observed on the entire film surface. The presence of a significant number of short-circuits was typical of the MIM structure based on such films together with a low electric strength of the dielectric film. It can be conjectured that changes in the electric properties and microrelief of the MIM structure surface are caused by the presence of carbon inclusions, and that the film porosity is nothing but simple carbon inclusions in the SiO2 film. However, studying the elemental composition by the method of Auger spectroscopy demonstrated the absence of carbon in the sputtered film structure. Hence, carbon inclusions cannot be a reason for changing the film relief. The results obtained by Troyan and Sakharov [1] and the results of the given electron-microscopic studies give us grounds to believe that the electric properties of SiO2 films change due to changes in the SiO2 film porosity. In our opinion, this is caused by the fact that carbon that associates with oxygen during sputtering of SiO2 + C films, leaves the SiO2 film as a CO or СO2 gaseous compound, thereby forming microscopic pores in the dielectric film and causing its porosity. Changes in the physical properties of the SiO2 films modified by carbon are caused by changes in the surface microrelief and the porous structure of the dielectric film.