Who would superior court judge report to?

I'm not familiar with the judicial system within any given state, but my cousin recently had a trial in Delaware where a superior court judge overseeing his case acted very unfairly and he wanted to pen a letter to someone at a higher level in the state judicial system, who would be more or less in charge of this superior court judge - who or what would that be in the court system? What title or position should he search for in sending the letter to the judge's superior ? Thanks for any help.