Energy-band-engineered unified-RAM (URAM) cell on buried Si_1-y C_y substrate for multifunctioning flash memory and 1T-DRAM

A band-offset-based unified-RAM (URAM) cell fabricated on a Si/Si_1-yC_ysubstrate is presented for the fusion of a nonvolatile memory (NVM) and a capacitorless 1T-DRAM. An oxide/nitride/ oxide (O/N/O) gate dielectric and a floating-body are combined in a FinFET structure to perform URAM operation in a single transistor. The O/N/O layer is utilized as a charge trap layer for NVM, and the floating-body is used as an excess hole storage node for capacitorless 1T-DRAM. The introduction of a pseudomorphic SiC-based heteroepitaxial layer into the Si substrate provides band offset in a valence band. The FinFET fabricated on the energy-band-engineered Si_1-y C_y substrate allows hole accumulation in the channel for 1T-DRAM. The band-engineered URAM yields a cost-effective process that is compatible with a conventional body-tied FinFET SONOS. The fabricated URAM shows highly reliable NVM and high-speed 1T-DRAM operations in a single memory cell.