Low frequency noise properties of the tunneling contact thin film transistors (TCT) have been studied in this work. An abnormal behavior of the normalized current noise power spectral density (PSD) which depends on the gate voltage with a slope~-3 is found. Numerical simulations show that threshold voltages of the current–voltage and capacitance–voltage characteristics are different owing to the unique device operation. A normal normalized PSD with slope~-1 recovers when the capacitance threshold is used. The dependence of PSD on drain voltage and channel length is also revealed. A slope~-3 of the channel length dependence different from the conventional one is explained.