Apache will attempt to keep idle processes running rather than constantly start new processes. Typically Apache config file is /etc/httpd/conf/httpd.conf or /etc/apache2/conf/httpd.conf. It does vary between distributions.
Change KeepAlive On -> KeepAlive Off
or if there is no KeepAlive option already simply add:
KeepAlive Off
Note: This will reduce RAM usage, but will increase CPU usage slightly as Apache will be starting new child processes more frequently.