A method of forming a photonic device structure comprises forming a photoresist over a photonic material over a substrate. The photoresist is exposed to radiation through a gray-tone mask to form at least one photoexposed region and at least one non-photoexposed region of the photoresist. The at least one photoexposed region of the photoresist or the at least one non-photoexposed region of the photoresist is removed to form photoresist features. The photoresist features and unprotected portions of the photonic material are removed to form photonic features. Other methods of forming a photonic device structure, and a method of forming an electronic device are also described.