Advantages:

Reduced leakage.

Excellent subthreshold slope.

Better voltage gain without degradation of noise or linearity.

Useful in digital & low frequency RF applications 5 GHz where performance power tradeoff is important.

Due to miniaturization trend the devices are being scaled down continuously giving rise to the short channel effects. As channel length shortens i.e. source and drain come closer, the gate voltage is not sufficient enough to efficiently control the current flow in channel region.

Due to leakage current existing in short channel, improving gate control is necessary.

This can be achieved using two gates, three gates or by surrounding the channel by gate, gate all around (GAA).