Nikon D7000 has a 16.0MP APS-C (23.6 x 15.7 mm ) sized CMOS sensor and features Expeed 2 processor. On the other hand, Nikon D700 has a 12.0MP Full frame (36 x 24 mm ) sized CMOS sensor and features Expeed processor.
Below you can see the D7000 and D700 sensor size comparison.
As seen above, Nikon D700 has a 2.3x Larger sensor area than Nikon D7000. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.