Many of the prior replies noted Transparent Data Encryption as an option. It was also noted that TDE encrypts the physical data files and not the data itself. The intent of this feature is to prevent someone from stealing your backup files or .mdf/.ldf files and restoring them on another server.
... This is what exactly my client's requirement.
"to prevent someone from stealing your backup files or .mdf/.ldf files and restoring them on another server."
Thank you all.