FinFET: Basics, Types (SG FinFET vs IG FinFET) Explained

This article delves into the fundamentals of FinFET (Fin Shaped Field Effect Transistor) devices. We’ll explore its basic principles, compare and contrast SG FinFET (Shorted-Gate FinFET) and IG FinFET (Independent-Gate FinFET) types, highlighting the key differences between them.

The core difference between a traditional FET (Field Effect Transistor) and a FinFET lies in the channel structure. In a FinFET, the conducting channel is wrapped around by a thin silicon structure, aptly named the “fin,” which constitutes the device’s body. The term “FinFET” originates from this distinctive characteristic. The fin’s thickness directly influences the effective length of the channel.

The wrapped gate design provides exceptional electrical control over the channel. This enhanced control effectively reduces leakage current and mitigates short-channel effects.

FinFET Types

FinFETs are broadly classified into two structural types:

• Single Gate Structure
• Double Gate Structure

Further categorization is based on the gate structure:

• Shorted-Gate (SG FinFET)
• Independent-Gate (IG FinFET)

Let’s examine the differences between SG FinFET and IG FinFET in detail.

Difference between SG FinFET and IG FinFET

Here’s a breakdown of the key distinctions between SG FinFET and IG FinFET devices:

• SG FinFETs:
  • Are 3-terminal devices.
  • Have their front and back gates physically connected (shorted).
  • Electrostatics of the channel are controlled collectively by both gates.
  • Tend to exhibit higher $I_{ON}$ (ON current) and $I_{OFF}$ (OFF current) compared to IG FinFETs.
• IG FinFETs:
  • Are 4-terminal devices.
  • Feature physically isolated gates.
  • Allow for different voltages to be applied to each gate, offering greater flexibility.
  • Enable linear modulation of the front gate’s $V_{TH}$ (threshold voltage) using the back gate bias.
  • Require more space due to the presence of two separate gate terminals.

Due to the advantages FinFET offers, it is widely used in :

• Design of RAM due to low off state current.
• Design of power amplifier(PA) or other analog circuits requiring good amount of linearity.