Created in the early 20th century during the Chinese pronoun reform. Just as 她 was coined for 'she' and 它 for 'it,' 祂 was created with the 示 (spirit/worship) radical specifically for referring to God in Christian Bible translations.
usage
Used exclusively in religious (primarily Christian) contexts. The radical 礻(示) relates to worship and the divine. In secular writing, 他 is used for all genders including deities.