Heat dissipation through device isolation

1. A structure, comprising:

an active device in a silicon substrate;

a dielectric film on said active device;

an isolation trench extending through said dielectric film and at least partially into said silicon substrate, said trench surrounding said active device;

a core in said isolation trench, said core comprising material having thermal conductivity greater than silicon dioxide and electrical conductivity equivalently comparable to silicon dioxide; and

thermal isolation fins connected to said core in said isolation trench and at least partially surrounding said active device.

2. The structure according to claim 1 , said active device comprising one of:

a heterojunction bipolar transistor (HBT);

a field effect transistor (FET); and

Bipolar Complementary Metal Oxide Semiconductor (BiCMOS).

3. The structure of claim 1 , further comprising:

a liner comprising an insulator material on sidewalls of said isolation trench.

4. The structure according to claim 1 , said material in said isolation trench comprising one of:

aluminum nitride (AlN), and

beryllium oxide (BeO).

5. The structure according to claim 4 , said thermal isolation fins comprising the same material as said material in said isolation trench.

6. The structure according to claim 1 , further comprising:

a shallow trench isolation (STI) structure in said silicon substrate, said trench extending through said STI structure.

7. The structure according to claim 6 , further comprising:

a barrier layer between said dielectric film and said STI structure, said barrier layer comprising one of:

nitride, and

oxynitride.