b 1. Field of the Invention
The present invention relates generally to semiconductor devices such as metal semiconductor field effect transistors (MESFETS) and, in particular, to the gate structure used for fabricating such devices.
2. Statement of the Prior Art
Metal semiconductor field effect transistors (MESFETS) are well known and widely used in many electronic applications and are constantly subject to examination and experimentation for purposes of improving performance characteristics and construction techniques. As with many semiconductor devices, a very significant area of interest lies in high-frequency performance to allow more extensive use of the device in microwave applications. In the particular area of field effect transistors, FETS, it is known that the capacitance present between the control gate and the source electrode limits the microwave frequency performance of the device, and therefore various efforts have been undertaken to reduce this gate-source capacitance. These efforts have varied from reducing the size of the control gate to reshaping the conducting region of the semiconductor to reduce the capacitance while still providing adequate current control through the semiconductor. If the control gate is reduced too much, its ability to cut off or pinch off all current flow through the semiconductor region is compromised, thusly deteriorating performance.
For these reasons it is an object of the present invention to reduce gate-source electrode capacitance while still providing proper current regulation by the control gate.