Once I play the game with my friends, I am always thinking what my character will be like in Arkham horror universe. Is there a tool available for people to make their own investigator?

Photoshop?

Check out Strange Eons software. Also, if you have a moment, check out my own custom investigators. The same characters with a similar background and theme are available for Arkham Horror, AH:LCG, and Eldritch Horror.

I made these early on in the life of the Arkham Horror card game, so the text on the cards is not completely in line with the wording in the official game, but the intent should be pretty clear.

(If anyone ends up deck-constructing with them, let me know what you think!)

https://boardgamegeek.com/filepage/142036/8-thematic-investigators

As mentioned already, Strange Eons. There is also a post on BGG with Photoshop/Gimp files that you can download to create custom cards. I will track down a link for that shortly.

Edit: I couldn't find the post on BGG, but I did find a link to the templates.

https://drive.google.com/file/d/0By2hzReltYWDYnZfSVhGVVliNzg/view

If you're looking for "rules" to assign stat lines and abilities and so forth, no, such a thing does not exist. It's not an RPG in that sense.

It's not terribly difficult to eyeball the basics, though, based on available gators.