How to ignore DOF with Sprite/default shader?

Hi all.

I'm having trouble with using DOF (image effect) and Sprite/Default shader object in the same scene.

please see the image: (you don’t have to think about stunning art visual...)

the cat's (Sprite/Default shader) right of face is blurring. I see, It caused from he doesn't write depth buffer. I turned on "Visualize" property of DOF component, it didn't show his shadow, as 2nd image.

It seems can solve with write his depth like as 3rd image (I painted).

so I wanna ask to you:

• How to handle to write depth buffer in Sprite/Default shader?
  I modified Sprite/Default shader Zwrite to On, but it won't work. (sorry for I'm new to shader programming)

• There is another way for ignore DOF for the sprite? (only DOF. other image effects are needed.)

Thanks for your time!