Intermediate layer and semiconductor package

Abstract

The purpose of this disclosure is to provide an interlayer that can prevent the peeling of an inner layer structure from an outer layer structure. To this end, the interlayer system disclosed herein comprises: an inner layer structure (7) including at least one inner wiring layer; a first outer layer structure (5) disposed on a first surface of the aforementioned inner layer structure; and a second outer layer structure disposed on a second surface of the aforementioned inner layer structure, wherein the aforementioned first outer layer structure (5) and the aforementioned second outer layer structure system have higher rigidity than the aforementioned inner layer structure (7), and have: a filling portion (21b) that fills a portion of the aforementioned first outer layer structure from the aforementioned first surface side of the aforementioned inner layer structure toward the inner side of the aforementioned inner layer structure; and / or a filling portion that fills a portion of the aforementioned second outer layer structure from the aforementioned second surface side of the aforementioned inner layer structure toward the inner side of the aforementioned inner layer structure.