How Flash Memory Works

Electronic memory comes in a variety of forms to serve a variety of purposes. Flash memory is used for easy and fast information storage in such devices as digital cameras and home video game consoles. It is used more as a hard drive than as RAM. In fact, Flash memory is considered a solid state storage device. Solid state means that there are no moving parts -- everything is electronic instead of mechanical.
Here are a few examples of Flash memory:

• Your computer's BIOS chip CompactFlash (most often found in digital cameras)
• SmartMedia (most often found in digital cameras) Memory Stick (most often found in digital cameras)
• PCMCIA Type I and Type II memory cards (used as solid-state disks in laptops)
• Memory cards for video game consoles

Flash memory is a type of EEPROM chip. It has a grid of columns and rows with a cell that has two transistors at each intersection (see image below).
The two transistors are separated from each other by a thin oxide layer. One of the transistors is known as a floating gate, and the other one is the control gate. The floating gate's only link to the row, or wordline, is through the control gate. As long as this link is in place, the cell has a value of 1. To change the value to a 0 requires a curious process called Fowler-Nordheim tunneling.