improvement is achieved

This is achieved if the emitter narrow dimensioned dielectric region or sidewall is determined from the "outside", rather than "inside", as shown in the above described process, the base contact windows can be reduced without change in device characteristics, and a 20 percent density improvement is achieved.
US Pat. 4400865

Of course, this improvement is achieved at the expense of some deterioration of image quality.US Pat. 5204756

Referring to FIGS. 6A and 6B, an example illustrating how a performance improvement is achieved by the present invention is shown.
US Pat. 5469560