Historical Engineers: Dr. Fujio Masuoka, the Unsung Father of Flash

December 02, 2022 by Chantelle Dubois

For the 35th anniversary of the invention of flash memory, here is a commemoration of the Father of Flash.

Few inventions have completely changed consumer electronics the way that flash memory has. The invention of flash allows us to carry pocket-sized devices such as smartphones with hundreds of gigabytes of storage that can read, write, and delete data in fractions of a second. At any given moment, a person with a smartphone has a repertoire of photos, videos, music, books, and other random data in their pocket. 

But it doesn’t stop there. Flash memory is everywhere: it’s in our laptops, our cars, even our washing machines. It would have been hard to imagine a world like that a few decades ago. 

Behind the invention is Japanese engineer Fujio Masouka. For the 35th anniversary of the invention of flash memory this year, here is a look at the so-called Father of Flash.


Fujio Masouka

Fujio Masouka, the “Father of Flash.” Image used courtesy of Honda


Masouka Sees a Bright Future in the Integrated Circuit

Masouka was born on May 8th, 1943 in Takasaki, Japan during World War II. During the Cold War, the world’s superpowers invested significantly in innovative technologies to maintain the high ground. Bright young students were attracted to the fields of physics, chemistry, mathematics, and engineering. 

Masouka was no different. When he started high school in Takasaki, he took a particular interest in mathematics and joined the school’s physics and electronics club. There, he learned about a new invention coming out of the United States: the integrated circuit. Masouka saw the integrated circuit as the future. It presented an exciting new world of possibilities in electronics that enabled computing to happen in much smaller form factors. Motivated by his newfound passion, Masouka earned university-level mathematics credits while still in high school to help his admissions application. 


Masouka in 1962 when he graduated from Takasaki High School.

Masouka in 1962 when he graduated from Takasaki High School. Image used courtesy of Honda


In quick succession, Masouka was accepted to Tohoku University and earned his Bachelor of Science, Master of Science, and Ph.D. in electrical engineering in 1966, 1968, and 1971, respectively. Just as he had wanted, he would specialize in integrated circuit technology.


Toshiba and the Invention of Flash

Shortly after completing his doctoral studies, Masouka joined the Toshiba Research and Development Center as a researcher in a small team.  

In the early 1970s, Toshiba was particularly interested in advancing non-volatile memory. Masouka later cited Intel’s presentation on non-volatile at the International Solid-State Circuits Conference as one of the motivating factors for the company to focus on this type of research.


International Solid-State Circuits Conference

The 1970 table of contents for the International Solid-State Circuits Conference lends insight into the state of electronics during the time when Masouka was finishing his final year of doctoral studies. Image used courtesy of IEEE


One of the first challenges Masouka tackled when it came to non-volatile memory was the speed at which data could be erased. In 1972, he and his team invented the stacked-gate avalanche-injection type MOSFET (SAMOS). Erasing the memory involved discharging the transistors using either UV light or electrically draining the charge. 


SAMOS memory cell

A SAMOS memory cell contains one control gate, and one is an isolated floating gate. Image used courtesy of the Toshiba Research and Development Center


In an update of the design in 1976, the SAMOS architecture was used to demonstrate write/erase on 2 kB of memory with a write time of 20 us and an erase time of 5 s. This speed resulted from the floating gate and the ability to use UV light to erase the charge. 

While the UV light provided a significant speed-up for erasing memory, it would likely be a limiting factor in widespread adoption. Masouka investigated ways to eliminate the UV light while maintaining performance. In 1984, he published details on flash EEPROM that “[erased memory cells] by using field emission of electrons from a floating gate to an erase gate in a flash.” The name “flash memory” came from a colleague who described the erasure process as happening “in a flash.”

Toshiba sold the first flash memory in 1987—although Intel would end up being credited as the technology's inventor and would profit significantly more on its own commercial flash memory. This fact was initially such an embarrassment for Toshiba that the company publicly conceded that Intel was the inventor to save face. 


Departure from Toshiba and Entrance to Professorship

After another decade with Toshiba, Masouka decided to accept a professorship at his alma mater, Tohoku University. He had received little recognition for his work at Toshiba and was increasingly feeling unsupported in his research.

At Tohoku University, Masouka ran his own research lab focusing on solid-state electronics. On his lab’s website, he emphasized the lab’s goals to perform useful research for humanity and the planet and saw large-scale integrated circuits as a key contribution, echoing his beliefs in high school that the integrated circuit was the future.


Masouka discovered NOR flash memory

In 1980, Masouka discovered NOR flash memory. Image used courtesy of Honda


Reportedly, Masouka would ask candidate students in interviews to imagine jogging and listening to all their music on a small device clipped to their ear—and that the work his lab did would help make that a reality. During the 90s, the world was still transitioning from the cassette Walkman to the CD-ROM Discman. MP3 players and smartphones were still over a decade away.

Despite moving on to his new role where he had much more control and support in his research, Masouka filed a lawsuit against Toshiba in 2004. Masouka wanted fair compensation for the work he had done for the company that had scarcely recognized his contributions. In 2006, Toshiba settled with Masouka for ¥87 million JPY (approximately $650,000 USD today). 


Masouka's Legacy Continues

After 11 years at Tohoku University, Masouka became CTO of Unisantis Electronics in 2005, a Japanese company specializing in surrounding-gate transistor semiconductor technologies. He still holds that role today at the age of 79. 


Masouka the engineer

In a lecture, Masouka once asserted, "I'm an engineer, not a researcher. However wonderful a thing you create may be, if it is expensive, nobody will use it. . . . Find something that does the job as a suitable price." Image used courtesy of Honda


On his IEEE authors page, his name continues to appear in publications as recently as 2021.  Even 35 years after the first commercial flash memory was sold, Masouka remains an important figure in semiconductor technology.