Abstract: An electrochemical sensor is described, containing a sensor substrate and at least one set of electrodes comprising a working electrode, a reference electrode and optionally an auxiliary electrode, further containing at least one reaction vessel, which is tightly connected to the sensor substrate and inside which is located at least one working electrode, whereas at least a part of the sensor substrate forms a vessel bottom. The vessel can contain a lid and also other preferred embodiments are described. The invention further describes a method of manufacture of the electrochemical sensor with the integrated reaction vessel, particularly by injection moulding.