How can replace some word with a real new line in Emacs?

[mgx0018]

Hello,
        In Emacs, What command can replace some word or symbol with a real newline.
For example, I have a text file like this:

int a;int b;intc;

After I exec the command that replae the ";" with ";" and new line, the text will like this:

int a;
int b;
int c;

      What command can do this? Thanks very much!!