No, not per se. It depends on the contract, if any, and the background default law. An intelligent IT company will have a contract with its employees that says, we own anything you invent on company time, and a nondisclosure agreement and a noncompete agreement too. But good tekkies and even good entrepreneurs are often clueless about the law. If there is no agreement, there may be background law, case law, statutes, in the jurisdiction that assigns rights to the parties. That is generally matter of state law. Or there may not, In which instance everyone can hire a lawyer and sue each other and we can go to court and have a merry old time of it. We bloodsucking leeches need to eat too, you know.