How to kill zombie process

I launched my program in the foreground (a daemon program), and then I killed it with `kill -9`, but I get a zombie remaining and I m not able to kill it with `kill -9`. How to kill a zombie process? If the zombie is a dead process (already killed), how I remove it from the output of `ps aux`? root@OpenWrt:~# anyprogramd & root@OpenWrt:~# ps aux | grep anyprogram 1163 root 2552 S anyprogramd 1167 root 2552 S anyprogramd 1169 root 2552 S anyprogramd 1170 root 2552 S anyprogramd 10101 root 944 S grep anyprogram root@OpenWrt:~# pidof anyprogramd 1170 1169 1167 1163 root@OpenWrt:~# kill -9 1170 1169 1167 1163 root@OpenWrt:~# ps aux |grep anyprogram 1163 root 0 Z [anyprogramd] root@OpenWrt:~# kill -9 1163 root@OpenWrt:~# ps aux |grep anyprogram 1163 root 0 Z [anyprogramd]