NOR flash memory has often been the shunned stepsister to the more popular NAND variety. But the tide may be turning, putting NOR in the spotlight at last.

Don't worry about what those acronyms stand for. All you need to know is that demand for NAND flash has grown strongly over the past few years, thanks to its increasing use in USB flash drives, memory cards for digital cameras, and in MP3 players like the Apple (NASDAQ:AAPL) iPod nano. While NAND flash is great as a nonvolatile storage medium -- your music and pictures don't disappear from it when the power is turned off -- NOR flash is used to store the executable code that powers digital devices. While demand for NOR flash has grown over time, it's grown much more slowly than demand for NAND flash.

NOR flash producers faced tough times in 2004 and 2005, and as a result, the big suppliers -- Spansion (NASDAQ:SPSN), Intel (NASDAQ:INTC), and ST Microelectronics -- avoided making large investments to expand capacity. Instead, they focused on improving their technology. As a result, the supply/demand situation for NOR flash may tip enough that NOR flash shortages could materialize this year, according to electronics industry research firm iSuppli.

Other data points also indicate that the future of NOR flash may be brighter than its recent past. While some speculate that Intel will sell its NOR flash unit, as AMD (NYSE:AMD) did last year, Intel denies this. Whatever its intentions, the company continues to invest in the NOR flash business; it recently became the first manufacturer to transition to 65-nanometer features.

Also, both Micron Technology (NYSE:MU) and Samsung appear to be committed to the NOR flash market. Both achieved sequential growth in their NOR flash units during the first quarter of this year, while the rest of the top 10 suppliers experienced sequential revenue declines.

If a lasting upturn materializes, Spansion shareholders stand to benefit. In the first quarter of 2006, the company had a 27.9% market share, just ahead of Intel's 26.7%. Spansion's price-to-sales ratio around 1.1 is very low for a semiconductor company, although it's probably warranted, given Spansion's need to prove it can make money. As a result, the stock probably has lots of room to run if business improves.

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Fool contributor Dan Bloom owns shares in Intel and Micron. You can reach him at [email protected]. The Fool has a disclosure policy.