A Study Of DC And AC Characteristics For Single Material Double Workfunction Gate MOSFET

In the past decade, RF circuit research had developed greatly which widely applied in wireless communication, medical treatment, remote viewing, global positioning and radio frequency identification. The working frequency of circuit quickly raised, and the requirements of high frequency characteristics for semiconductor devices had become much highed. In recent years, it is unceasing reported that the frequency of the MOSFETs which are made up of semiconductor material such as SiGe, SiC or SOI new structure can reach some hundreds GHz,and show certain advantages in high frequency, high temperature and high power field. But, these techniques must be based on advanced and complex manufacturing technology, so their application will be limited commonly.Nowadays, silicon CMOS technology is still the trend of microelectronics. The proposed Single Material Double Workfunction Gate(SMDWG) LDD MOSFET using pure silicon whose gate have been designed is considered as a new RF structure having excellent performance. The gates consist of S-gate with high workfunction p+ polysilicon and D-gate with low workfunction n+ polysilicon and are parallel to each other. In the SMDWG MOSFET, the threshold voltage near source is greater than it near drain, the step-function profile in the surface potential exhibits improvement in screening of the drain potential variation. The peak in the electric field distribution along the channel ensures more uniformity in the average drift velocity of the electrons and improves current, transconductance and cut-off frequency.The thesis starts with an introduction of MOSFET's knowledge, analysing the challenge of mini-sizing the devices and improving the structure. Then it reveals the structural designing and technical processing of SMDWG-LDD MOSFET. And the process of SMDWG MOSFET is simulated by Suprem software. Finally, By simulating, the effects of the parameters are studied, which include the gate length,gate oxide thickness and channel doping density. Meanwhile, compared with the single doping polysilicon gate MOSFET, the new structure has an improved performance and the obtained result is of some guidance to the structure design manufacture and performance optimization which indicates n+/p+ MOSFETs have good application prospects in RF field.