Kill zombie process in Linux

When a process in Linux dies, process’s status becomes EXIT_ZOMBIE and its parent is notified that its child has died with sending SIGCHLD signal.The parent process then executes wait() system call and get process exit status. on successful execution of wait(), the zombie process exits completely from memory. Otherwise it remains as zombie process.
Zombie process stores very tiny amount of system memory to store its process descriptor.
Command to get list of zombie processes running

ps aux | awk '{ print $8 " " $2 }' | grep -w Z

Above command will display something like:
Z 8960
Z  = Zombie
8960 = process PID

Killing the zombie process is not easy.try killing it by following command

kill -9 8960

This probably wont kill it.Now try to find out the parent process of this process.

pstree -H 8960 -p

Now kill the parent process.
kill -9 1649

This should kill the zombie process.