US Patent 7598560 Hetero-bimos injection process for non-volatile flash memory

A hetero-BiMOS injection system comprises a MOSFET transistor formed on a substrate and a hetero-bipolar transistor formed within the substrate. The bipolar transistor can be used to inject charge carriers into a floating gate of the MOSFET transistor. This is done by operating the MOSFET transistor to form an inversion layer in its channel region and operating the bipolar transistor to drive minority charge carriers from the substrate into a floating gate of the MOSFET transistor. The substrate provides a silicon emitter and a silicon germanium containing base for the bipolar transistor. The inversion layer provides a silicon collector for the bipolar transistor.