Existing experimental data for the temperature dependence of 1/f noise in both n- and p-channel MOS transistors are heuristically compared with either bulk or surface phonon spectra or with both of them. It is found that the noise structure mirrors different van Hove singularities in both bulk and surface phonon spectra. This is thought to be the signature of surface and bulk phonons in the 1/f noise of MOS transistor. For a Debye phonon spectrum, an intriguing 1/τ distribution is obtained. The famous connection between oxide states and 1/f noise can be understood in terms of phonon scattering if the tunneling is inelastic. Striking similarities were found in the temperature dependence of the frequency exponent in different MOS transistors and all of them feature similarities with those of the frequency exponent in silicon on sapphire. This indicates that a common structural factor is controlling the temperature variation in both systems. Starting from the observation that the noise intensity vs. temperature is the image of the phonon density of states, the temperature dependence of the frequency exponent was calculated. It is in a reasonable agreement with the experiments for both n-channel transistors and silicon on sapphire sample.
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