Abstract: A layer of base material has a film layer and a barrier layer on the film layer, and also adhesive tape has the base material and an adhesive layer on the barrier layer. Thus, they do not have any fish-eye or foreign substance on their surfaces, so that accuracy in thickness are improved and contamination of a material to be adhered with the adhesive layer is also improved.

Abstract: A base material has a radiation-cured material prepared by curing a mixture of urethane acrylate oligomer and reactive dilute monomer, and also it shows a breaking elongation of more than 10%, preferably of more than 100%. The base material is used as a base sheet of an adhesive tape where an adhesive layer is formed on the base sheet. Accordingly, the novel base material and its manufacturing method in addition to an adhesive tape having such base material are provided. Furthermore, the adhesive tape has a flat surface without any fish-eye that causes the troubles of cracking, chip-scattering, and so on in the steps of back-grinding and dicing of the semiconductor wafer, and also the adhesive tape can be processed so as to have a predetermined thickness with high accuracy, compared with that of the conventional one.