Why does only negligible gate current flow,in a depletion-mode MOSFET,even when the gate voltage is positive?

Question

Quizplus · Accepted Answer

The metallic gate in a depletion-mode MOSFET is insulated from the channel by a thin layer of silicon dioxide (SiO2) or another insulating material. This insulation prevents significant current from flowing into the gate, even when a positive voltage is applied, making the gate current negligible.

Why Does Only Negligible Gate Current Flow,in a Depletion-Mode MOSFET,even