This paper describes a new sealing structure, a “floating nested structure”, for flexible hybrid electronic (FHE) device applications using an ultrathin chip (UTC). In the floating nested structure, the part on which the UTC is mounted is physically connected to the sealing material only with a meander structure. By using the floating nested structure, the tensile strain transmitted to the UTC mounted on a flexible substrate can be reduced markedly. We fabricated a UTC with a thickness of 5 µm using deep reactive ion etching (deep-RIE) technology. The fabricated UTC had flexibility with a radius of curvature of 0.5 mm. Also, we conducted an experiment to demonstrate the effect of the floating nested structure. When the elongation of the test sample used in the experiment was 20%, the strain on the flexible substrate without the floating nested structure was 710 µε. In contrast, the strain was 220 µε when using the flexible substrate with the floating nested structure. This means that the floating nested structure reduced the propagation of strain by 69.0%. From the above results, it is expected that the floating nested structure can be useful in the development of FHE devices with both elasticity and flexibility.