Is it compulsory to have a master's degree in computer science for research jobs?
It is highly unlikely that you'd get a permanent research position in CS with a bachelor's degree. It's also unlikely (though not impossible) that you'd get one with an MS degree (for example, it might be possible to enter an organization after an MS, and then move internally into their research wing). The most common path to getting a research job at an institute is after a Ph.D.