Two memory chips each being subjected to memory accesses in 2-bit units are assembled into a stacked structure by placing their back surfaces one over the other, so as to make memory accesses in 4-bit units. A memory module is so constructed that a plurality of such semiconductor storage devices, in...http://www.google.de/patents/US20030075789?utm_source=gb-gplus-sharePatent US20030075789 - Semiconductor storage device having memory chips in a stacked structure
