The physical origin of the excess thermal noise in short channel MOSFETs is explained based on numerical noise simulation. The impedance field representation and extraction method demonstrate that the drain current noise is dominated by source side contributions. Analysis identifies local ac channel resistance variations as the primary controlling factor. The nonlocal nature of velocity results in a smaller derivative of the velocity with respect to the field which in turn causes a higher local ac resistance near the source junction. Index Terms---Hydrodynamics, MOSFETs, semiconductor device modeling, semiconductor device noise, simulation. I.

First of all, I would like to express my sincere appreciation for my research advisor, Professor Ali Hajimiri, for his guidance and support over this five year journey. I would like to thank him for bringing me into the High-Speed Integrated Circuits Group at Caltech, where I have been able to work in my most favorite research field. Inspirations drawn from the fruitful and enlightening technical discussions with him have helped me overcome plenty of difficulties encountered in the design and experiments and have been crucial in making those projects successful. I am especially grateful for his constant encouragement, which will continue to promote my desire to do my best in my future career. I would like to thank Professor David Rutledge and Dr. Sander Weinreb. I have learned a lot in the technical discussions with them. Their valuable suggestions as well as support in providing test equipments in the Caltech Microwave Laboratory have appreciably accelerated the progress of my research projects. I feel very lucky to have worked with the current and previous members of Caltech

This paper identifies the physical origin and contribution mechanism of substrate induced channel thermal noise in MOSFETs. Resistance of the substrate generates potential fluctuations that in turn produce additive channel noise via the channel depletion capacitor. The additive noise may result in a frequency dependence of the drain current noise due to a pole associated with the R sub -C depl network. Its bias and length dependencies conforms to those of reported excess noise, it thus may exaggerate the amount of the channel thermal noise factor. 1