Gate leakage
Beginner
Electricity that sneaks straight through the super-thin insulating layer inside a transistor, a layer only a few atoms thick.
Novice
Current that tunnels through the gate insulator when it is only a few atoms thick. It flows whenever a voltage sits across the gate, whether or not the transistor is switching.
Expert
Direct tunneling current, exponential in oxide thickness. It became a major leakage term as gates thinned toward roughly a nanometer, and is the reason high-k gate dielectrics replaced : a thicker high-k layer gives the same capacitance with far less tunneling.