| 摘要 |
PURPOSE:To improve the writing speed of a P-N-P cell type ECL RAM, by making the impurity concentration of an epitaxial layer in a cell forming region larger than the impurity concentration of an epitaxial layer in a peripheral- circuit forming region. CONSTITUTION:The impurity concentration of a memory-cell forming part 14a of an epitaxial layer on an ECL RAM substrate is made high. Another pert 14b of the epitaxial layer is a region for forming a peripheral circuit for the RAM and a bonding pad. The concentration of impurities at this part is as usual. In this constitution, since the concentration of the N-type impurities in the epitaxial layer (collector regions of Q3 and Q4) of a memory cell is high, the recombination speed of holes (minority carriers) generated in the current conducting state becomes high (time change dp/dt of holes is proportional to electron concentration (n)). Therefore, increase in collector potential Vc of a transistor on the ON side becomes quick, and a writing time DELTA becomes short. |
