Patch Factorio executable so that it runs in true fullscreen mode when fullscreen is selected. What factorio currently uses is a windowed fullscreen (maximized borderless window). True fullscreen has potential to increase performance and enables you to play at different than desktop resolution, but can cause more problems and slows done alt-tabbing.
Check fullscreen in Factorio, run the patcher, select the Factorio executable from the Steam folder, select the resolution, click patch and run Factorio.
Currently tested with 0.15.5 on Steam, 0.14 or Linux will definitely not work, while other 0.15 versions or non-Steam ones might work.
Binary can be downloaded from the github release page (https://github.com/rkapl/factorio-true-fullscreen/releases).