The drawback of double diffused transistor process?
Answers
Thus, this process is similar to the situation with respect to the base width of a double-diffused bipolar transistor. ... This will help in making enough space for the expansion of the depletion region between the p-type diffusion region and the n+ drain contact region.
The figure below shows a double-diffused MOS (DMOS) structure. The channel length, L, is controlled by the junction depth produced by the n+ and p-type diffusions underneath the gate oxide. L is also the lateral distance between the n+ p junction and the p-n substrate junction. The channel length can be made to a smaller distance of about 0.5 micro meters. Thus, this process is similar to the situation with respect to the base width of a double-diffused bipolar transistor. When a fairly large positive voltage is applied to the gate [>VTH], it will cause the inversion of the p-substrate region underneath the gate to n- type , and the n-type surface inversion layer that is produced will act as a conducting channel for the flow of electrons from source to drain.