eSTM embedded Select in-Trench Memory

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eSTM: a step forward in 40nm embedded NVMs

Non-volatile memories (NVMs) are required in embedded devices to store data after they have been turned-off. Charge storage NVMs hold an electrical charge in a memory device for storing data. They are used in most industrial, consumer, and automotive applications today. To further improve the footprint, cost, and performance of general-purpose and secure microcontrollers, ST introduced the industry-first embedded Select in-Trench Memory (*) (eSTM) cell in a 40nm node.

* is a registered and/or unregistered trademark of STMicroelectronics International NV or its affiliates in the EU and/or elsewhere.

In 2015, within less than two years after the R&D project was initiated, eSTM technology was successfully developed in a 40nm node and ready for wide-scale production. Since 2017, 15 ST products have been produced implementing this technology and many more are being designed and validated. Today, billions of end devices have been commercialized based on this technology, thanks to ST’s investment and manufacturing facilities.

* is a registered and/or unregistered trademark of STMicroelectronics International NV or its affiliates in the EU and/or elsewhere.

From technology to industrialization

From banking cards to mobile phones, from hearing aids to industrial robots, eSTM technology is used in billions of devices around the world. eSTM technology is implemented in embedded and standalone memories today, enabling significant improvements in application performance.

eSTM in NVMs: setting a new standard in EEPROMs

ST’s 8 to 32Mbit NVMs, called the Page EEPROMs, are based on an eSTM cell in a 40nm node. This technological leap reduces die size and allows for:

  • memory densities beyond the market-reference 4Mbit EEPROM.
  • energy savings during read, erase, and programming operations (up to 5 times less energy consumed compared to industry standards)
  • faster erase commands (10 times faster than industry standards)
  • more cycling endurance (5 times more than industry standards.)

In many devices, such as medical hearing aids, using an eSTM cell in the NVM results in significant improvements to the user experience and expands device battery life.


eSTM in general-purpose microcontrollers: improving STM32 performance

Many STM32 MCUs, such as the high-performance STM32H5, implement eSTM technology in a 40nm node.

The eSTM cell is the smallest Floating Gate embedded NVM cell in a 40nm node in the industry today, which enables significant cost savings. Using eSTM technology in STM32 also improves MCU and application performance by enabling faster erase times and a higher cycling capability for data Flash, up to 10 times more compared to the previous generation, as it is the case for the STM32H562/63 MCUs.


eSTM in secure microcontrollers: enabling a cost-efficient architecture

STSECURE microcontrollers with a built-in eSTM cell can address a wide range of applications, from consumer devices to automotive applications with the most stringent requirements. The tiny eSTM cell in a 40nm node allows for significant space and cost savings in secure microcontrollers. eSTM also offers the flexibility of an EEPROM with the memory density of a flash memory.


A unique cell architecture

eSTM is based on a unique cell architecture. An eSTM cell consists of a storage element structured as a conventional stack of a polysilicon floating gate (FG) and a polysilicon control gate (CG), as well as a vertical select transistor (wordline). 

The select transistors (wordline) of two adjacent cells are merged together into a single structure and placed vertically in the depth of the silicon reaching an underlying n-doped diffusion which plays the role of source line.

eSTM cell cross section.


Going further: read our technical publications

40nm embedded select in-trench memory technology overview


Embedded select in-trench memory (eSTM), best in class 40nm floating gate-based cell: a process integration challenge