A 16-Level-Cell Nonvolatile Memory with Crystalline In-Ga-Zn Oxide FET

A 16-level cell is demonstrated using a test chip of nonvolatile oxide semiconductor RAM comprising c-axis aligned crystalline In-Ga-Zn oxide FETs. A read circuit composed of voltage followers outputs a read voltage with a maximum distribution of 37 mV. A single voltage follower has a maximum distribution of the read voltage of 25.3 mV. A 200 ns write time of the test chip is demonstrated.