MESFET transistor with air layer between the connections of the gate electrode and the substrate and the respective fabrication process

Claim 2

1) A Schottky barrier metal-semiconductor field effect transistor (MESFET) including a substrate, a gate electrode, which the input signal is fed to, a drain electrode to take the amplified output signal and a source electrode, characterized by the fact that the gate electrode (G) is made up of one body having the shape of a continuous sheet which by-passes through the air a portion of the source electrode and is soldered to the substrate at a side of the said portion with a bump contact and, at the other side of the source portion, along a line corresponding to all the longitudinal extension of the sheet, which has such an area that the resistance of the gate electrode is negligible

Claim 3

2) A transistor according to claim 1, characterized by the fact that the source electrode has an I shape, i.e. it includes two heads having a big transversal extension and a connection segment between the said heads having a small transversal extension but a great axial extension and the gate sheet has a longitudinal extension little less and a transversal extension much higher than those of the said source segment by-passed thereby.

Claim 4

3) A transistor according to claim 1, characterized by the fact that the drain electrode has an axial - extension little higher than that of the gate sheet and a transversal width of the same order of magnitude as the source segment by-passed through the air by the gate sheet.

Claim 5

4) A transistor according to the previous claims, characterized by the fact that the major side of the drain is parallel, facing and slightly separated from the soldering line of the gate by-pass end to the substrate.

Claim 6

5) A transistor according to the previous claims, characterized by the fact that the gate and drain bump contacts are centered onto the respective bodies, have areas of the same order of magnitude and are located at opposite sides with respect to the longitudinal source segment.

Claim 7

6) A transistor according to the previous claims, characterized by the fact that the gate and drain with their external central bump contacts are substantially specular with respect to the connection segment between the source heads.

Claim 8

7) A process for the fabrication of MESFET transistors according to the previous claims, characterized by the fact that: - the active area is derived from the substrate and the source and drain contacts are implemented thereon; - a photomasking process is made to define the gate electrode and the respective connection bump contact; - a major portion of the metallization (Ti-Pd-Au) between the source and the drain is made evaporate and an electrolytic growing is made, for instance using gold, up to the desired thickness (for instance 2 to 10 micron); - a second photomasking process is made to define the bridge connection or air by-pass of the gate onto the central source segment; - finally,the total metallization is etched (gold removal) in that area located above the drain electrode, so as to leave the soldering line of G in the free zone between D and S G and simulta- neously the photoresist materials are removed, so as to implement the air by-pass gate connec- tion to the source.