Structures and methods are provided for determining operating characteristics of a non-volatile memory transistor comprising a charge-storage-layer and a tunneling-layer. In one embodiment, the method comprises: forming a structure including a charge-storage-layer overlying a tunneling-layer on a substrate; depositing a positive charge on the charge-storage-layer and determining a first voltage to establish a first leakage current through the charge-storage-layer and the tunneling-layer; depositing a negative charge on the charge-storage-layer and determining a second voltage to establish a second leakage current through the charge-storage-layer and the tunneling-layer; and determining a differential voltage by calculating a difference between the first and second voltages. Other embodiments are also disclosed.