A semiconductor memory device has memory cells, each including an emitter region formed in a base region as a bit line, a barrier layer formed in a hole formed in the oxide layer to be in contact the emitter region, a high resistance layer formed thereon, and a metal wiring layer as a word line in...http://www.google.de/patents/US4424578?utm_source=gb-gplus-sharePatent US4424578 - Bipolar prom
