Im, no sound artist, but in case you get no better answers...
Yes, if possible, real sounds are collected, and then run through filters to perhaps soften or whatnot or changes are made to the beginning or end to make them repeat nicer. Just the same way textures are done.
Many sound people like to just record many weird things, and play with the frequencies in many weird ways. Sometimes you get something that sounds like something else in real life. Then this sound gets used for a laser blaster or whatnot. At this point, because the device doesnt really exist, we just associate that sound that some guy made with the fictional device and that is what we expect thereafter. So in order to find out most of the scifi sounds you will probably have to speak with a seasoned sound developer or use one from a sound collection.
You could just grab yourself a nice sound wave editor, start playing with the frequencies, and see what you can come up with though.