An ethics department is like a human resources department, but for broader ethics related matters.
HR: Ostensibly exists to support the employees, but really exists to shield the company from both a PR and legal liability standpoint when the company has a rift with one or more employees.
Ethics Department: Ostensibly exists to make sure the company acts ethically, but really exists to shield the company from both a PR and legal liability standpoint when the company acts unethically.
It is a good personal signal that you have never worked for a company with an ethics department or an ethics employee. The less ethical your company the more likely it is to have an ethics department.