Random telegraph signal (RTS) noise shows discrete and stochastic switching in two or more states at a drain current or threshold voltage. The capture and emission of carriers in individual traps near a silicon-gate insulator film interface induce RTS noise phenomena. RTS noise has become a crucial problem in analog devices and other devices. To suppress RTS noise, it is necessary to determine the energy level of traps. Time constant ratio has a strong relationship with the energy level of traps in gate insulator films. In this paper, we extract a large number of RTS data sets with large-scale array test patterns and evaluate the gate-bias voltage dependences of time constant ratio and amplitude. We demonstrate that the energy level of traps distributes uniformly at a drain current of at least 0.1-1.0 μA.