(Dice.com chart)

Competition for tech workers continues to heat up, according to the latest survey from Dice.com that says the surge in hiring has pushed the tech unemployment rate below 4 percent in the U.S. (The overall U.S. jobless rate is 9.1 percent).

With so many tech companies hiring, positions are staying open for months due to a shortage of qualified technology professionals. According to Dice.com, 63 percent of those surveyed say talent shortages are the primary reason. Six months ago just 46 percent blamed unfilled jobs on talent shortages.

Dice surveyed about 900 hiring managers and recruiters. According to the survey, 65 percent anticipate hiring more technology professionals in the second half of 2011. The survey was reported by CDNet.

Nearly half the companies (47 percent) say salaries are higher than a year ago. That’s up from 29 percent six months ago, according to Dice.

The survey reflects what local employers have been seeing for a while. When I talk to tech executives, most all are hiring. However, most all still seem upbeat about their chances of continuing to land top talent.

Some major Silicon Valley employers have made hiring more competitive in this region. Google has doubled its staff in Kirkland in the last two and a half years to 800 employees. Facebook has a staff of 40, according to the WSJ.

Related coverage: Why Facebook, Google and Zynga are flocking to Seattle