1. Field of the Invention
This invention relates to integrated circuit structures and processes for manufacturing them, and in particular to an improved power metal oxide semiconductor field effect transistor (MOSFET) structure having higher switching speeds and improved breakdown characteristics.
2. Description of the Prior Art
Continuing improvements in integrated circuit fabrication technology have lead to the manufacture of MOSFET's which are capable of efficient high frequency switching of relatively large amounts of power. The power MOSFET represents one of the first power semiconductor devices manufacturable using integrated circuit processing technology. A survey article discussing power MOSFET's is entitled "Switching Lots of Watts at High Speed" by B. Baliga, IEEE Spectrum, December 1981, pages 42-48.
One promising technology for the manufacture of advanced power MOSFET structures is VDMOS, meaning MOS devices fabricated using double diffusions in V-shaped grooves. Unfortunately conventionally fabricated VDMOS structures suffer from several disadvantages. Such devices are generally overly susceptible to secondary breakdown of parasitic bipolar transistors inherent in the structure. Furthermore, such structures typically have undesirably large drain to source resistance when on. In addition, the devices switch at undesirably low speeds in view of their relatively large size and therefore high gate capacitances.