Who ended Charlemagne's empire?

After the death of his son the empire was divided between his (Louis, the sons of Charlemagne) three sons, as was common in his culture. De title of "holy Roman Emperor" was given to the most eastern part, today known as Germany.

That is also the reason that Germany was known as "the Holy Roman Empire" until 1806. So it was his son who first divided his empire, but it existed until 1806.