I have been taking on extra responsibilities that I did not have when I was hired. I am being introduced as a "specialist" now that I have extra training and believe that shows that my position has changed.
What are the company's policies regarding the frequency and timing of employee reviews? Start by checking your employee handbook and make sure you completely understand the policies. You then have a decision to make: you can approach your boss to discuss the matter and try to work it out, you can talk to your HR professionals to ask them to address it on your behalf, or you can wait and ask if any adjustment to your compensation can be made retroactively, in light of the delay. Each strategy carries risks. The first two risk impacting your long term relationship with your boss. The last strategy is a financial risk but preserves the relationship. You have to ultimately decide what's most important to you, and what consequences you're willing to live with. Happy to talk with you directly if I can be of more help.
I would take a way different angle. I believe your employer already knows you are due additional compensation and that is why it is getting put off. Maybe they don't have current resources to give you what they deserve so he is kicking the can down the road.
What I would do is walk up to him/her and say "Name, I want you to know that I am really excited about how I have grown and developed here and hope that as part of our next step we can sit down together and plan a long career path so I can continue to be a bigger asset for you. I know your very busy but this is a priority to me, would it be possible to set a firm time/date we can stick to right now?
Don't let the employer stave off having the conversation with you, its a poor leadership tactic and doesn't show respect for the work you have performed or the amount you have grown. I am sure he isn't avoiding conversations with you about other things...