You can't fix it, it's by design. The reason for having each tab in a separate process is so that a catastrophic error in one tab doesn't crash the whole browser, just that tab. It's also more efficient for performance reasons, it means that a high CPU intensive tab doesn't stop a less CPU intensive tab from getting CPU time (because each process - actually each thread - queues individually on the CPU dispatcher queues).
One disadvantage of using multiple processes is that it uses more RAM, but in modern systems where 16GB of RAM is common that's a small price to pay for reliability and performance.
Disclaimer: I'm not advocating for Chrome you understand, just pointing out why it uses multiple processes.