Is D3000 compatible with nikon sb700 flash?

And if ever they're compatible, Can i take the flash ( sb700 ) out of the hot shoe and use it as a slave?

Yes, the SB-700 should be compatible. If you are unsure, you should search on the net for info or ask a nearby photo store.
The SB-700 can be used as an optical slave for any camera with built in flash, since it reacts on any flash that is fired as long as the SB-700 is set to "SU-4" mode in the menu. In that option, it will be able to be triggered by the D3000 but you will have to set all flash options manually on the flash itself since D3000 doesn't have an advanced master flash mode for the built in flash.

Yes, the D3000 is compatible with the SB700 (as long as it is attached to the hot shoe), and No it can't be used as a slave in iTTL.

Your D3000 does not have the required Nikon CLS commander circuitry. You have two options; either a SC-29 cable which gives you a 10ft range, or a SU-800 which sits atop your hot shoe and allows you to use the Nikon CLS system.