SF
You aren't supposed to read Crichton and think he's SF. You aren't supposed to think he's thriller, either. You're supposed to think he's mainstream. This, at least, is the goal of his publisher.
You can, in truth, classify darned near anything as thriller, or as technothriller, and bookstores often do. But for me, at least, real technothrillers use real technology, or at least technology that is currently feasible, if not in active use. At the outside, it uses technology that could be built right now, if we wanted to do so. Clancy does this. So do all the techno-writers I read. Crichton usually does not.
Crichton uses speculative technology. His novels pretend the technology is real, or currently feasible, but most of it isn't. Most of it lies firmly in the future, and a good bit of it will probably never be real.
Many hard SF writers do use the same techniques Crichton uses, and their novels are indistinguishable from his.
The only element necessary to make something SF is that the story itself be speculative, and makes use of technology that is also speculative. With Clancy, we read about technology that is, with Crichton, we read about technology that might, or might not, someday be. This is the hallmark of science fiction. As opposed to sci-fi, of course.
The only Crichton novel I've read that I'd classify as techno-thriller is The Andomeda Strain.