When you remove an Android widget from your home screen, you don't uninstall it from your phone and it still uses some memory. To uninstall Android widgets from your Android phone or tablet, do as follows:
1. Open "Settings" and go to "Application Manager" (On some devices, Apps)
2. Go to "All" tabs and tap the Widget to uninstall
3. Hit "Uninstall" and confirm the process
Note that, since some Android widgets do not show up in the App Drawer, you can not uninstall them from there, and you have to do as mentioned.