Different default permission for directory and file

Question

I want to set a different default permission for new directory and file. For example, default directory permission is 770 (group members can write things to the directory) but default file permission is 640 (not allow group members to delete/modify the file). How can it be done? (I know umask can be used for setting default file/directory permission but it will make both directory and file having the same permission.) Thanks.