A united expression for the doping concentration of both p-regious and n-regions of the CB (Composite buffer)-stucture with different pat-terns is derived and used for solving Poisson's equa-tion. The physical parameters are then obtained and can be used to optimize the CB-structure of any pat-tern under a given breakdown voltage.

The optimized values for the physical and ge-ometrical parameters of the p-and n-regions used in the voltage-sustaining layer of the COLMOSTM2 are presented. Design of the parameters aimed to produce the lowest specific on-resistance. Ron.for a given breakdown vnltage. Vp.A new relationship between the Ron and Vv for the COOLMOSTM IS developed as Ron=cv1.32, where the constant Cis dependent by putting a thin layer of insulator between the p-region and its neighboring n-regions, the value of Ron can be further reduced. The possibilry of incorporating the insulating layer may open up opportunities for practical implementation of the COOLMOSTM fof volume production.

The hexagonal pattern of the voltage-sustaining layer in the COOLMOST with p-region in the center of cach unicell, which produces the lowest specific on-resistance, is studied based on a technologically achievable minimum aspec ratio of the width of each region to the thickness of the voltage-sustaining layer. A breakdown voltage higher than th previouw result is also achieved by breaking the requirement of the different peak fields to be equal. Futhermore, thdoping of the p-region near the drain is modified to get a better result It is believed that this is the new theoretica "Silicon Limit". The results show that a value Of Ron less than 1/3 of the previous one is obtained. Theoretical analysis given and shows in good agreement with the numerical simulation.

A novel high-voltage generic power device structure based on an optimum variation in the lateral doping profile is proposed. The structure is implemented with a series of zones having piece-wise constant doping located in the field sustaining region of the device. The structure has been evaluated as an integrated component in a range of high-voltage devices, including MOST, JFET and BJT, The simulation results show the breakdown voltages achieved by the different structures can reach 85% of that, calculated for an equivalent parallel plane abrupt junction, The on-resistance of each device is very low while he switching speed is very high. Among these devices, the Most shows the best improvement in performance, Since these lateral devices are compatible with modern sub-micrometre IC-tech-nology, and are capable of self-isolation, they are very attractive for applications in HVIC and PIC processes.

Results of some new inventions of voltage sustaining structure for both vertical and lateral power devices are presented. A figure of merit is defined for appreciating the devices which show that the nes devices are much better than the prior arts.