So you want to completely disable all function of capacitive buttons?
If so, using a file explorer (I recommend ES File Explorer), navigate to /system/usr/keylayout and find two files named "himax-touchscreen.kl" and "snyaptics-rmi-touchscreen.kl"
open up those files as text and put a hash symbol (#) to every line of those files
Example, in himax-touchscreen.kl, it should look like this in the end:
#key 102 HOME
#key 158 BACK
Save it and do the same for the other file. Reboot and the capacitive buttons should stop functioning now. If you want to get the capacitive buttons back, just remove the # symbols on those files and reboot