The dominant noise contributors in short-channel CMOS devices at radio frequencies are:
1. Channel thermal noise
The Channel thermal noise of mosfet is described by:
(in)^2=4kTγgdo
For long channel devices, the excess noise factor (γ) is 2/3. However, for short channel devices this factor can be higher.
2. Induced gate noise
3. Parasitic gate and bulk resistance – those resistance are due to finite sheet resistance of the semiconductor materials can add to the overall noise floor of the MOSFET at high frequencies and if overlooked can easily become the dominant noise contributor for the device. It can be minimized by scaling the aspect ratio, adding fingers to the gate, and by contacting both ends of each finger of the transistor.
