Is there a way to build a 2k*12 RAM using only 2 4k*4 Chips
The only way to increase the apparent width of a physical memory is to wrap it in a sequential circuit that executes multiple cycles internally for each external read or write cycle. This requires a means of multiplexing the data during write cycles and demultiplexing it during read cycles.

For example, you could turn your 4k &times; 8 physical memory into a 2k &times; 16 virtual memory by storing each 16-bit word in two consecutive 8-bit locations in the physical memory. The physical memory would execute two read or write cycles internally for each external cycle.