[yodsanklai]

> But I would work may unpaid extra hours at home

I think that's incorrect. You would work the number of hours you wish to work (considering you produce reasonable value, but the bar is low). Research engineer (or researcher for that matter) in a public French research center is a civil servant position. They are difficult to get but you don't get fired unless something is blatantly wrong.

Source: I worked 10+ years in such a position. I work now for a FAANG and the pressure is considerably higher. Evaluations every 6 months, lot of peer pressure (engineers are on average better and more ambitious than those in academia and you need to keep up - some of them seem to work 24/7), extremely stressful oncalls. Gross salary is 5 times my previous salary and has the potential to increase much more.

Of course, this is certainly not representative of all cases, but most of the time, there's a price to pay for a higher salary. Another thing to think about is ageism: as a research engineer in academia, you're all set until retirement. In software industry, it's getting hard after 50.