Closing a window in OS X Yosemite causes other windows to be made active I have a Chrome window and this Chrome window covers the whole screen (not in the full screen mode, though). I also have 5 Finder windows under this Chrome window. So I can't see any Finder windows. Now I need a Finder window, so  I use Mission Control. Everything works well, but when I close this Finder window, other all Finder windows show up on top of the screen, I don't need them, I only need one window.

How can I prevent this? 

This is happening all apps. Not just in Finder and I am using Yosemite 10.10.
This is the Apple paradigm - all windows belonging to one app are part of a single process, unlike Windows, which is, as the name suggests, windows-based. Apple is App-based. What you are seeing is intended behaviour.

The simplest 'workaround' - though to me an indispensable way to use the machine - is to enable Spaces &amp; the associated hot-keys, then put 'important' apps on a Space of their own &amp; switch using the hot-keys. 

[I'm in the middle of teaching someone how to use that method right now in meatworld - a Windows migrant learning the new paradigm - so if you're interested, I'll try to flesh out exactly how to go about it.]