Consider the following statements regarding MOS circuit design process:

1. MOS circuits are formed on four basic layers : n-diffusion, p-diffusion, polysilicon and metal, which are isolated from one another by thick or thin silicon dioxide insulating layers.

2. Thin oxide (thinox) mask region includes n-diffusion, p-diffusion and transistor channels.

3. Polysilicon and thinox regions interact so that a transistor is formed where they cross one another.

Which of the above statements are correct?

Key Points

MOS Layers:

MOS circuits are formed by three layers i.e. diffusion ( n or p diffusion layer), polysilicon, and metal, which are isolated from one another by thick or thin (thinox) silicon dioxide insulating layers.

• The thin oxide region includes n- diffusion, p- diffusion, and transistor channels.
• Polysilicon and thinox regions interact so that a transistor is formed where they cross one another.
• Layers may be deliberately joined together where contacts are formed.
• The basic MOS transistor properties can be modified by the use of an implant within the thinox region.