This paper investigates the emission and capture kinetics of random telegraph signals (RTS) in MOSFETs. A modified two-step approach is proposed which includes the capture of a carrier by trap located at the Si-SiO2 interface, followed by a tunneling process of the trapped carrier between the interface trap and a trap located in the SiO2 layer. In this case the quantum transitions represent a primary process which involves three basic states. In some cases this can be approximated by a two states g-r process X2(t), which coincides with a secondary process Y(t) representing current modulation. It is shown that by this model a quadratic dependence of the capture rate on the drain current can be explained, provided that the quasi-Fermi level at the surface is below the interface trap level. From the presented model the ratio of interface trap cross-section and oxide trap cross-section determines the capture and emission time.