In an active area surrounded with an isolation formed on a silicon substrate, a large number of unit cells are disposed in a matrix, and the unit cell together form one MOSFET. Each of the unit includes a ring gate electrode in the shape of a regular octagon, a drain region and a source region formed...http://www.google.co.uk/patents/US6140687?utm_source=gb-gplus-sharePatent US6140687 - High frequency ring gate MOSFET
