MOS Transistor
		This is an example of an MOS transistor, (on-off button).. The area between the source and the drain is able to conduct electricity or act as an insulator depending on the voltage applied to the gate, which is how the on-off signal is kept by the transistor.          To simplify this, the center of the transistor acts as a capacitor.  The gate and the p-type silicon act together to be electrical conductors and the silicon dioxide layer acts as an insulator.         When there is a lack of gate voltage to induce a charge build-up in the p-type silicon near the silicon dioxide interface, the p-type silicon acts as an insulator and currents aren't able to pass.  This is when the transistor is in the off state.          When a positive voltage is applied to the gate, negative charges build up in the p-type silicon near the dilicon dioxide interface which creates a conductive pathway between the two n-type regions for electrons to flow from the source ot the drain.  This is when the transistor is in the on state.