The microstructure of La2/3Ca1/3MnO3 films of 42-nm thickness, grown on (001) SrTiO3, (001) LaAlO3 and (001) Y-stabilized ZrO2 substrates, has been studied with considering the existence of surface/interface dead layers. The dead layer thickness deduced from X-ray reflectivity is in good agreement with that from transport property measurements. Due to the surface and interface layers, the spontaneous emergence of fully relaxed and coherently strained films is further demonstrated by grazing incidence X-ray diffraction. The smallest saturation magnetization and the largest coercive filed is obtained in La2/3Ca1/3MnO3 film grown on LaAlO3 substrate, which has the thickest dead layer thickness. Moreover, the effect of dead layer on the magnetic and transport properties of La2/3Ca1/3MnO3 film grown on Y-stabilized ZrO2 substrate has been carefully analyzed.