Regular expressions syntax: is \ the escape character ?

Hi,

I'm using regular expressions in 6.5.3 version but i cannot find the
character to escape special caracters as ?, $, ^.

I've tried with \ but it doesn't works.

Example: i want to find the row with the value 'fisica?' and i do:

select title from libros where title ~* 'fisica\?' ;

but i also obtain rows with values:  'fisicamente' or 'fisicas'

What am i doing wrong ?

Thanks in advance.

Gabi :-)