The given figure represents a semiconductor device. Let's identify the device based on the terminals and the symbol provided.

In the diagram:

• G stands for the Gate terminal.
• D stands for the Drain terminal.
• S stands for the Source terminal.

The symbol shown here is of a Junction Field Effect Transistor (JFET). A JFET is a type of Field Effect Transistor (FET) that controls the electrical current by using an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material.

Let's evaluate each option to understand why it's not the correct choice:

1. Zener Diode: This is used for voltage regulation and has a different symbol usually depicted with an angled Z at the cathode.
2. Silicon Controlled Rectifier (SCR): This is usually a 3-terminal device but arranged with an anode, cathode, and gate, differing from the diagram shown.
3. Tunnel Diode: Known for its tunneling effect and has a symbol different from what's shown in the image.
4. Junction Field Effect Transistor (JFET): As explained above, the symbol matches a JFET, with these specific terminals (Gate, Drain, Source).

Conclusion: The correct answer is junction field effect transistor based on the symbol and terminal arrangement.