Transistors Transistors Transistors are the building blocks of computing and communications electronics. The region of silicon between the source and the drain can conduct electricity or act as an insulator depending on the voltage applied to the gate.
Pure silicon is a poor electrical conductor at room temperature.
The extra electrons, or the missing electrons, can make doped silicon an electrical conductor under the right conditions. An electrically conducting gate material, often polycrystalline silicon, is then applied above the exposed p-type region. Another layer of insulating silicon dioxide is applied, and conductive pathways to the game and n-type regions are etched into this later. By changing the voltage on the three electrical connections, the transistor can act as an insulator or it can pass electrical current from the source to the drain. To understand how a MOS transistor works, think of the center slice of the transistor as a capacitor.