Current cancer treatments such as surgery, radiation and chemotherapy have significant side-effects for the patients. New treatments are being developed to reduce these side-effects while giving doctors alternative methods to treat patients. This invention introduces a new apparatus for treatment of malignant tumors including brain cancer, pancreatic cancer, lung cancer, ovarian cancer, and breast cancer. The apparatus couples RF power into the tumor using evanescent waves. The evanescent waves disrupt the division of cancer cells causing the cancer cells to die and shrink the size of the tumor. Due to the targeted approach of the evanescent waves, less RF energy is wasted in healthy cells.