*Question G6A09:
Which of the following describes MOSFET construction?*  

*Correct Answer is  B: The gate is separated from the channel by a thin insulating layer*  

### AI Response: (may contain errors)  

The correct answer to the question about MOSFET construction is:

**B: The gate is separated from the channel by a thin insulating layer.**

### Explanation of the Correct Answer:
- In a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), the gate is indeed separated from the channel (the region where current flows) by a thin layer of insulating material, typically silicon dioxide (SiO₂). This insulating layer is crucial because it allows the gate to control the channel's conductivity without direct electrical contact, enabling the MOSFET to function as a switch or amplifier.

### Why the Other Choices are Incorrect:
- **A: The gate is formed by a back-biased junction.**
  - This statement is incorrect because the gate of a MOSFET is not formed by a back-biased junction. Instead, it is typically made of a metal or heavily doped polysilicon that is insulated from the channel.

- **C: The source is separated from the drain by a thin insulating layer.**
  - This is incorrect because the source and drain are not separated by an insulating layer. They are both connected to the channel and are typically made of the same semiconductor material, allowing current to flow between them when the MOSFET is turned on.

- **D: The source is formed by depositing metal on silicon.**
  - This statement is misleading. While metal contacts can be used in the source and drain regions, the source itself is typically formed by doping silicon to create a semiconductor region, not merely by depositing metal.

### Summary:
- The key feature of a MOSFET is the insulated gate, which allows for control of the channel without direct electrical contact. Understanding the construction and operation of MOSFETs is essential for grasping their role in electronic circuits.