Junction shortening-type semiconductor read-only memory.

摘要

In a junction-shortening type PROM, between a pair of memory cells (MC), a highly doped region (12) of the same conductivity type as the base is provided. This region (12) is a base contact region leading out the paired bases commonly out to the surface terminal connected to a word line (W₀ W₁,...). This region (12) reaches the substrate (SUB), the collector, so as to reject influence between the paired cells by pre­venting the minority carriers in each of the paired bases from diffusing into each other base. The base contact region (12) may be isolated from the emitter regions (26) by a narrow groove filled with an insulation material deeper than the emitter but shallower than the substrate (SUB). A cell block composed of the paired cells and the base contact region (12) is isolated at its circumferences by a narrow groove (22) filled with a dielectric insulating material. The narrow isolation grooves and the elimination of the conventional buried base layer reduce stray capacity and increase the current amplification factor of the transistors. Both of them allow the related circuit to require less current load, which means increasing switching speed or less power consumption, and also reduction of occupation area for cells and the peripheral circuit, resulting in in­creased density of integration.