The process of  reduction of threshold voltage of the transistor at higher drain voltages is called as

The process of reduction of threshold voltage of the transistor at higher drain voltages is called Drain Induced Barrier Lowering (DIBL).

Here are the steps that explain this process:

1. When a voltage is applied to the drain of a MOSFET, it creates an electric field within the device.

2. This electric field extends into the channel region and affects the barrier height at the source end.

3. As the drain voltage increases, the electric field strength also increases. This causes the barrier at the source end to lower.

4. This lowering of the barrier at the source end due to the influence of drain voltage is known as Drain Induced Barrier Lowering (DIBL).

5. DIBL effect causes the threshold voltage of the device to reduce with an increase in drain voltage. This is because the lowering of the barrier allows more carriers to be injected from the source into the channel, thus turning on the device at a lower gate voltage.

6. DIBL is a short-channel effect, which means it becomes more pronounced as the channel length of the MOSFET is reduced. It is a major concern in the design of modern ultra-small devices because it can lead to increased leakage current and power consumption.