Aim of this work – to show the possibility of oscillation chaotization at the effect of low- frequency (0.1...3.0 MHz) noise signal both on feed circuit of IMPATT diode in one-frequency IMPATT diode oscillator (IMPATT-DO) and on feed circuit of transistor in one-frequency transistor oscillator. It supposed to confirm the assumption, said early, that this effect, found by us in first time for one-frequency IMPATT-DO, can take place for any semiconductor oscillators with p–n-transition, more exactly, it’s nonlinear current-voltage characteristic. Method. The microwave Сolpitts oscillator with a simplified structure was created for decision of this problem. The Si–Ge p–n–p-transistor was used in the oscillator as an active element. The same (0.1...3.0 MHz) noise signal oscillator was used for the effect on it’s feed circuit as in experiment with IMPATT-DO. The deterministic oscillation regimes (one-frequency and two-frequencies) of the microwave Сolpitts oscillator were investigated. Subsequently the low-frequency noise signal effect on the feed circuit of transistor was investigated and the spectra comparison of the microwave generation was leaded without an effect and with it. This comparison has shown in first time the deterministic oscillation spectra has transformed to chaotic oscillation spectra in microwave Сolpitts oscillator at the low-frequency noise signal effect on the transistor feed circuit. Result has full confirmed our assumption. Therefore this effect can take place for any semiconductor oscillators with an active element, which has p–n-transition, more exactly, it’s nonlinear current-voltage characteristic.