Technical Glossary

A technical glossary that covers terms related to KIOXIA products and technologies, such as memory and SSDs. We explain that it can be used by engineers and researchers to the general public.

Words starting with “B”

Bad block

Blocks that are judged to be unsuitable for data storage at the manufacturing stage, or blocks that have a large number of memory cells that have been deteriorated due to an increase in the number of data writes. Because no data is stored in a bad block, the more bad blocks, the less data can be stored in the chip.


KIOXIA’s products with ECC circuits in SLC NAND flash memory. It is possible for customers to use 24nm SLC NAND flash memory technology even when their platform cannot support higher bit ECC, because error correction is not necessary by host computer side.


KIOXIA’s 3D flash memory. In order to reduce the cost of manufacturing flash memory, rather than stacking memory cells from one layer and one layer below, we have applied a breaking method of creating memory cells in all layers at once by stacking plate-shaped electrodes, forming holes through them, and passing through the electrodes.


A unit of data processed by a computer. “1bit” indicates the minimum amount of data that can be expressed in binary.

Bit cost

Manufacturing cost per bit

Words starting with “C”


Computer-aided design, a method of drawing or designing a product on a computer. The TCAD used in simulation for device and process for semiconductor devices is a type of CAD.

Client SSD

SSDs used in a variety of fields, including PCs, tablets, entry-class servers, and IoT/embedded devices.

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A substance with low electrical resistivity that is easy to pass electricity through, such as metal.

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A logic semiconductor that plays a role in controlling NAND, DRAM, etc. Controls the reading and writing to memory, such as management of bad blocks, wear leveling, and error correction.

Control gate

Words starting with “D”

Data Center SSD

SSDs mainly used in data centers. It is suitable for low-end servers and cloud data centers that require both low power consumption and high performance.

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Design rule


Among semiconductor memory, one of the volatile memory that loses data recorded in the memory cell when the power is turned off. Data can be read and written very quickly compared to flash memory. It is mainly used for PCs, servers, and smartphones. (Dynamic Random Access Memory)

Words starting with “E”

EB (Exabytes)

The unit of memory capacity. 1EB=260B (approximately 1billion GB)


One of the standards for flash memory with built-in controller. Small, low power consumption and high capacity, and can be incorporated into tablets, smartphones, etc. (Embedded Multi Media Card)

Enterprise SSD

SSDs used in places where high performance and reliability are required, such as enterprise IT infrastructure and bank remittance systems. They improve data protection, safety and confidentiality.

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Error correction

Detect and correct errors that occur when writing data to memory or other storage media or sending or receiving data. The code used for this function is called ECC (Error Correction Code).


Removing unnecessary portions to form a circuit pattern on a wafer. There are two ways to remove: “wet etching” using chemical solutions, etc., and “dry etching” using reactive gas, etc.


KIOXIA’s personal product brand.

Words starting with “F”

Film formation

The process of forming a layer on the surface of a wafer as a material for semiconductor circuits, such as insulating films or metal films.


KIOXIA’s SD memory card with embedded wireless LAN function.

Flash memory

It is one of the non-volatile memories in which data in the memory cell remains even when the power supply is turned off, and data can be written and erased repeatedly. There are two types of flash memory: NAND type and NOR type. KIOXIA invented world's first memory in 1984.

Floating gate

A layer between a gate and a silicon substrate in a memory cell of flash memory. By applying voltage to the gate, it is possible to create both states; full electrons or no electrons in the floating gate.

Words starting with “G”


Terminal to which voltage is applied mainly to control the operation of transistors and memory cells. In the memory cell of flash memory, applying voltage to the gates can allow electrons to move into and out of conductive charge storage films and signals to be read.

Gate electrode

GB (Gigabyte)

The unit of memory capacity. 1GB=230B (approximately 1,000MB)

Words starting with “H”

HDD (Hard Disk Drive)

One of the electronic components that records data. A storage device that records data by placing a magnetic head against a disk. It features a higher capacity and lower price compared to SSD. (Hard Disk Drive)

High integration

Integrating elements with multiple different functions on a silicon substrate. The integrated electronic components are called IC (Integrated Circuits), and as the degree of integration increases, they are called LSI (Large Scale Integration) and VLSI (Very Large Scale Integration).

Words starting with “I”


A substance with a high electrical resistivity that conducts little electricity.

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Words starting with “L”


Forming a circuit pattern on a wafer. The photosensitive material (resist) is applied to the wafer, a photomask with a formed circuit pattern is layered, and a light source is applied to transfer the formed circuit pattern to the wafer.

Words starting with “M”

Mbit (Megabit)

The unit of memory capacity. 1Mbit = 220bits (approximately 1million bits)

Memory cell

The smallest unit of memory where information is stored in a memory chip, which itself acts like a cubicle. Data is recorded according to the amount of electrons in the memory cell (cubicle).

Metal gate electrode


A memory cell that can store 2bits of data in a single memory cell. (Multi Level Cell)

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microSD Memory Card

One of the recording media for data, which is recorded by using flash memory. It is smaller than SD memory card, and is used in small devices such as smartphones, tablets, drones, and drive recorders.


Technology that reduces the processing dimensions of elements and wiring on wafers. Miniaturization in semiconductor memory refers to a technology in which a single memory cell occupies as little space as possible and contains as many memory cells as possible in a single flash memory.

Moore’s Law

Gordon Moore, one of Intel’s founders, advocated the semiconductor integration rate law in 1965. In general, it is said that “the integration rate of semiconductors doubles in 18months.”

Multi-level cell technology

Technology that increases the amount of information that can be stored in each memory cell. Depending on the amount of information that can be recorded in one cell (number of bits), it is called MLC (2bit/cell), TLC (3bit/cell), and QLC (4bit/cell).

Words starting with “N”

NAND flash memory

A type of flash memory. By connecting memory cells in series, it can realize higher density and larger capacity than NOR type. KIOXIA invented world’s first NAND flash memory in 1987.


Units expressed “nm” representing one billionth of a meter. The minimum size of memory cells in a typical 2D NAND flash memory is about 1/4000 hair at about 15nm in recent years.

NOR flash memory

A type of flash memory. Memory that allows for random access and fast data readout by connecting memory cells in parallel.

Words starting with “P”


Plastic resin that protects chips equipped with electronic circuits from heat, light, shock, etc.

PB (Petabyte)

The unit of memory capacity. 1PB=250B (approximately 1million GB) 



In the lithography (exposure) process, this is the first step for transferring patterns of electronic circuits to silicon wafers. A fine circuit pattern is formed on the transparent quartz glass plate.

Power Loss Protection (PLP) Function

Data protection in case of power loss situation on SSD. Using the power charged to on-board capacitors inside of SSD, even in case of power loss situation, the recorded data can be retained and data on the cache that has just been received can also be recorded in flash memory.

Process rules

Minimum unit dimensions for processing circuits and wiring when manufacturing semiconductors. It is mainly used to represent the generation of semiconductor manufacturing.

Words starting with “Q”


A memory cell that can store 4bits of data in a single memory cell. (Quad Level Cell)

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Words starting with “R”

Random read

One of the data readout methods that directly links to memory performance and speed, and reads the data while skipping the order. On the other hand, the readout methods that continuously reads data in sequence are called sequential reads.


The ability of the product to meet the required specifications for a specified period of time under specified conditions. In flash memory, it is expressed as the failure rate in relation to the number of times the data can be written and the retention period. The higher the reliability, the longer the product life.

Words starting with “S”

SD memory card

One of the recording media for data, which is recorded by using flash memory. It is larger than microSD memory card, and mainly used for digital cameras, video cameras, laptops, etc.


Material with an electrical resistivity between conductor and insulator. The electrical resistivity changes significantly due to temperature changes, voltages, magnetic fields, light irradiation, and the addition of small amounts of impurities. There are mainly germanium and silicon in semiconductor material, and silicon is used as a material for semiconductor products such as memory.

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Sequential access

Sequential read

One of the data readout method that is directly linked to memory performance and speed, and which continuously reads data in sequence. On the other hand, reading data while skipping the order is called a random read.

Silicon wafer


A memory cell that can store 1bit of data in a single memory cell. (Single Level Cell)

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SSD (Solid State Drive)

One of the storage devices used in PCs, data centers, work equipment, etc. It consists mainly of NAND flash memory, DRAM and the controller that controls them. It is resistant to vibration and shock, lightweight, and low power consumption.

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Stacking/stacking process

A technology that increases the number of memory cells per unit area by stacking a planar structure of memory cells on top. Stacking allows for large memory capacity.

Storage Class Memory (SCM)

Non-volatile memory that can perform high-speed processing by complementing the gap between the performance and capacity of the main storage (DRAM) and storage (flash memory and SSD).

Words starting with “T”

TB (Terabyte)

The unit of memory capacity. 1TB=240B (approximately 1,000GB) 


A system used in simulation for device and process for semiconductor devices. Especially in the development of advanced memory, new materials and complex three-dimensional device structures need to be developed, so TCAD is used to efficiently advance development. (Technology Computer Aided Design)

Thin film formation


A memory cell that can store 3bits of data in a single memory cell. (Triple Level Cell)

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An element that controls current, such as amplification of electrical signals and ON/OFF.


Electrodes that penetrate the front and back surfaces of silicon wafers (silicon penetration electrodes). In addition, it is a technology to connect multiple chips at the shortest distance, enabling high density integration. (Through-Silicon Via)

Words starting with “U”


One of the standards for flash memory with built-in controller. Read and write faster than eMMC. (Universal Flash Storage)

USB Flash Drive

A storage device that reads and writes data directly to a USB port on a PC. (Universal Serial Bus)

Words starting with “W”


It is a semiconductor single crystal disk that serves as the basic material for all semiconductor chips, including flash memory. In recent years, it is common to have a diameter of 300mm and a thickness of about 1mm made of silicon single crystals for memory. The silicon is purified to form a high-purity, single-crystal ingot (cylinder-shaped chunk of silicon) and thinly sliced.

Wear leveling

Technology for preventing deterioration due to writing of data in storage media such as flash memory, and extending the product life. Prevents deterioration by controlling the writing of data so that it is evenly distributed rather than concentrated in one place.

Words starting with “X”


KIOXIA’s low-latency and high-endurance storage class memory (SCM). Non-volatile memory with lower bit cost than existing DRAM and higher capacity like NAND flash memory. A memory cell type of XL-FLASH™ is SLC, which enables fast read and write speeds.


KIOXIA’s removable PCIe®/NVMe™ memory device. It is smaller than SD memory card and adopts a new form factor with minimal height (size 14mm × 18mm × 1.4mm, area 252mm².) It is intended to be incorporated into devices and used as a boot drive, and is suitable for applications such as ultra mobile PCs.

Words starting with “Numbers/Symbols”

3D flash memory

Flash memory that increases the number of memory cells per area by stacking a flat structure of flash memory on top. KIOXIA announced the world's first 3D flash memory technology in 2007.