Professor Chen is very highly thought highly of by his students.

thought 是动词 think 的过去分词形式，think 意思是"思考、认为"。 highly 是副词，由 high（高的）加后缀 -ly 构成，表示"高度地、非常"。 of 是介词，表示"关于"。 thought highly of 是一个固定短语，字面意思是"被高度评价"，实际表示"受到高度赞扬/好评"。