Semiconductor device

1. A semiconductor device comprising:

a semiconductor layer;

an active region defined in the semiconductor layer;

first fingers provided on the active region and arranged in parallel with respect to a first direction;

second fingers provided on the active region and interleaved with the first fingers;

a bus line that is provided on an outside of the active region and interconnects the first fingers;

first air bridges that are provided on the outside of the active region and are extended over the bus line, and that are electrically connected to the second fingers; and

second air bridges that are provided on the outside of the active region and are arranged in a second direction which crosses to the first direction, and that are electrically connected to the first air bridges,

wherein the first fingers are gate fingers and the second fingers are source fingers or drain fingers,

wherein the first air bridges and the second air bridges are connected at a cross point, the cross point is located at the first air bridge, and the cross point is separated from a surface of the semiconductor layer by air.

2. The semiconductor device according to claim 1 , wherein:

the second fingers are composed of a lower interconnection layer on an ohmic electrode and an upper interconnection layer provided on the lower interconnection layer in the active region in the semiconductor layer;

the first air bridges are formed by only the upper interconnection layers; and

the bus line is composed of a gate interconnection layer and the lower interconnection layer provided on the gate interconnection layer.

3. The semiconductor device according to claim 1 , wherein:

the second fingers have a structure that includes an interconnection layer on an ohmic electrode in the active region in the semiconductor layer; and

the first air bridges have a thickness equal to that of the interconnection layer.

4. The semiconductor device according to claim 1 , wherein the second air bridges connect center portions of the first air bridges.

5. The semiconductor device according to claim 1 , further comprising:

fixing portion provided outside of outermost one of the first air bridges; and

third air bridges interconnecting the fixing portions and the outermost ones of the first air bridges.

6. The semiconductor device according to claim 5 , wherein the second finger connected to the outermost one of the first air bridge is an outermost finger in the second fingers.

7. The semiconductor device according to claim 5 , wherein the third air bridges are connected to center portions of the outermost ones of the first air bridges.

8. The semiconductor device according to claim 1 , wherein a ratio of a length of the first air bridges to a product of a thickness and width thereof is 0.1-0.6.

9. The semiconductor device according to claim 1 , wherein the bus line and the second air bridges are overlapped.