Abstract
The noise of n- and p-channel S. O. S.-M. O. S. transistors has been measured at room temperature in the range of 1 kHz-1 MHz. Its behaviour has been related to the doping of the silicon film and to the effect of the bulk silicon layer bias. n-channel devices and p-channel ones, with a high enough doping concentration, exhibit 1/f noise which tends to the theoretical thermal level at higher frequencies. This noise is thought to be due to the Si-SiO2 interface levels. p-channel devices with a fully depleted silicon film present bumps in the noise spectra which are superposed on a 1/f background. They are associated with three different levels in the depletion zone and also near the lower interface. Making simple assumptions in the theory of G. R. noise in M. O. S. transistors, a density of traps of about 10 11 cm-2 for each level has been found. These noise measurements have been made in connection with threshold voltage measurement, the variation of which confirms the complete depletion of the silicon film.