4. Floating-Gate 1Tr-NOR eFlash Memory

In this chapter, we will highlight the peculiar features of one of the most popular implementations of the embedded flash cell: the so-called 1Tr-NOR. The one-transistor cell has been by far the most adopted cell architecture in the world of flash NOR stand-alone memory. As an almost natural consequence, 1Tr-NOR architecture has also been considered the first, and for sure one of the best, solutions in embedded non-volatile memory (NVM) applications and has been progressively replacing EEPROM cells. In this chapter, only embedded multi-megabit flash implementation will be reviewed: different solutions for 1Tr-NOR flash cell structure and design architectures have been successfully implemented and will be described. In particular, the focus hereinafter is based on the description of how the unique features offered by that cell can be efficiently and effectively integrated into MCUs, which represent one of the major fields fueled by embedded flash capability. In the following sections, after a short introduction devoted to highlighting some peculiar technology features related to 1Tr-NOR integration with state-of-the-art CMOS, three different kind of MCU products will be thoroughly analysed: