▎ 摘　　要

NOVELTY - The gas sensor has a detection layer (2) which is provided on a lower metal electrode (1) and detects gas. A top metal electrode (3) is provided on the detection layer. The detection layer is equipped with a barrier layer (21) which consists of material with an electron affinity smaller than a work function of a graphene. A first graphene layer (22) is laminated on the barrier layer. The top metal electrode is provided so that the first graphene layer is partially exposed. USE - Gas sensor e.g. oxide semiconductor gas sensor, chemical substance sensor, expiration gas sensor and graphene gas sensor, and applied to medical treatment and diagnostic apparatus. ADVANTAGE - The gas of the concentration of parts per billion (ppb) level is detectable by high sensitivity like the concentration of the gas molecule in expiration air. The contribution to the health maintenance and medical cost containment in the future aging society can be anticipated. The discovery and diagnosis of the disease can be enabled. The performance to detect the trace amount gas molecule in expiration air is realizable. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for manufacturing the gas sensor. DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the gas sensor. (Drawing includes non-English language text) Lower metal electrode (1) Detection layer (2) Top metal electrode (3) Barrier layer (21) First graphene layer (22)