In English, the first letter of a sentence after a semicolon does not need to be capitalized, because the semicolon connects two independent clauses into one sentence.
An independent clause is a string of words that can become a complete sentence. When you want to join two complete sentences into one long sentence, you can add a semicolon between them.
Example: This could be a complete sentence; this could be another one. (For example: This could be a complete sentence; this could be another one.)
If you use a comma where a semicolon should be, you have committed "comma sticking", which is a very annoying grammatical error. Sometimes the second clause doesn't really look like a complete sentence, so you have to watch it closely.
Example: Twelve workers started the project; only five remain. Exceptions may cause you problems. You can join two complete sentences without a semicolon, as long as a conjunction (and, but, etc.) is used between the clauses. In this case, only a comma is required.
The semicolon has two main uses in English, both of which are easy to recognize. The first is to join two independent clauses into a single sentence, and the second is to act as a super comma. In addition, there are some special uses of semicolons that are rarely seen, but there are other ways to deal with these situations. To a certain extent, the standardization of English writing is closely related to the reasonable use of semicolons.
Reference: Semicolon-Baidu Encyclopedia