Layoffs
The semiconductor industry in general is very cyclical. Typically, you will see raging good-times of profit and revenue only to be followed a couple/few years later with massive losses and everybody's worst fear: layoffs. Sometimes, the bad-times aren't bad enough to trigger mass layoffs, but it's always a concern when the stock or revenues start getting too low for Wall Street's comfort.
During a layoff, you might see entire groups get let-go, certain individuals fired, or even entire geographical sites shut-down. Rumor of the imprending doom often leaks around the cube-farm in advance of the actual announcement which leads to everyone worrying and lots of water-cooler talk about what's going to happen.
Fortunately, or as fortunately as you can get being laid-off, semiconductor companies generally have pretty decent severance packages. A severance package is given when a valued employee is let-go during one of these downturns and generally will include a certain base payment amount, pay-out for remaining earned vacation time, and an amount of money determined by the number of years they have worked at the company. For example, a company might offer two weeks of pay base plus one week per year of service. For short-term employees, this can be a fairly small amount, but for "lifers" who have worked at a company 15 or more years, it can be quite a tidy sum.
Of course, not all companies will give severance packages, especially if the company is a start-up or is doing extremely badly (i.e. nearing bankruptcy). However, most larger companies will always attempt to offer some package so they can avoid a bad reputation among the workforce. After all, that company will probably be hiring like mad during the next upturn in the semiconductor cycle and they want to have engineers interested in working there or the chips don't get designed!