Charge trapping effect in silicon-rich oxide (SRO) films was investigated using capacitance versus voltage (C–V), current versus voltage (I–V) and current versus time (I–t) measurements in an Al/SRO/Si MOS-like structure. SRO layers with different thicknesses were deposited. The trapped charge density was found to depend on the thickness of the SRO layers. It was shown that the total trapped charges can be divided into two parts: one part is correlated with the Si nanoclusters located near the SRO/Si interface (interface-NCs); another one is correlated with the Si nanoclusters distributed in the bulk of the SRO layers (bulk-NC). A current peak was observed in the I–V curves in the surface inversion condition. The peak position voltage varies with the thickness of the SRO layers. The current peak is attributed to the charging/discharging of the interface-NCs. The charging/discharging process of interface-NCs was evidenced by a fast decay of current in I–t measurements at the current peak voltage. I–t curves recorded at a large positive voltage are associated with the charge trapping effect of the bulk-NCs. The Coulomb blockade effect was suggested to be the reason of current decay at constant voltage.