An image sensor module having a sensor chip closely adhered on a concave surface and a fabrication method thereof are disclosed. The image sensor module includes at least one sensor chip, at least one sensor chip-mounting structure comprising a substrate and a polymer layer formed on the substrate, the polymer layer having an concave surface formed on an upper part thereof by a polymer molding method, so that the sensor chip is bent and bonded on the concave surface, and at least one lens fixed on the at least one sensor chip-mounting structure above the sensor chip.