TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The inorganic material is silicon dioxide (SiO2), aluminum oxide (Al2O3), calcium carbonate (CaCO3), titanium dioxide (TiO2), silicon sulfide (SiS2), silicon phosphate (SiPO4), magnesium oxide (MgO), zinc oxide (ZnO), barium titanate (BaTiO3) and natural or organically modified clay.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polyethylene is single or combined polyethylene having ethylene or ethylene and 3-8C alpha -olefin and having melting temperature of greater than or equal to 125 degrees C; polypropylene is single or combined polypropylene having propylene or propylene, ethylene and 4-8C alpha -olefin having melting temperature of greater than or equal to 160 degrees C; and heat-resistant filler having melting temperature of greater than or equal to 170 degrees C. The heat-resistant resin is polyvinylidene fluoride, polymethylpentene, polyethylene terephthalate, polycarbonate, polyester, polyvinyl alcohol, polyacrylonitrile and polymethylene oxide, and inorganic material having average particle size of 0.01-5 mu m. Preferred Contents: The polyethylene layer comprises more than 50% of the total thickness and polypropylene and heat-resistant filler layer has thickness of approximately 1 mu m. The polypropylene and heat-resistant filler layer comprises 20-50 wt.% of polypropylene and 80-50 wt.% of heat-resistant filler. Preferred Property: The film has thickness of 9-30 mu m, puncture strength of greater than or equal to 0.2 N/ mu m and permeability of 2.5x 10-5-10x 10-5 Darcy; preferably puncture strength of greater than or equal to 0.15 N/ mu m, permeability of greater than or equal to 1.5x 10-5 Darcy and melt fracture temperature of greater than or equal to 170 degrees C, with micropores of polyethylene layer fabricated by stretching and extracting after separating phase of polyethylene and diluent and having average size of less than or equal to 0.1 mu m; and macropores of the polypropylene and heat-resistant filler layer fabricated by cracking of interface between polypropylene and heat-resistant filler and having average size of 1-50 mu m. EXAMPLE - In layer 1, polyethylene having weight average molecular weight of 3x 105 and melting temperature of 134 degrees C and paraffin oil having kinetic viscosity of 95 cSt at 40 degrees C were used, and proportion of the two components was 20 wt.% and 80 wt.%, respectively. The thickness of the layer 1 sheet prepared was 2000 mu m. In layer 2, polypropylene having a weight average molecular weight of 2.5x 105 and melting temperature of 163 degrees C and barium titanate (BaTiO3) having an average particle size of 0.4 mu m were used, at 20 wt.% and 80 wt.%, respectively. The thickness of the layer 2 sheet prepared was 80 mu m. The layers 1 and 2 were heat fused to make 3-layered structure in the order of layer 2, layer 1 and layer 2, and stretched simultaneously at 122 degrees C to total stretching ratio of 49 times, 7 times in longitudinal direction and 7 times in the transverse direction. The film thickness was 30 mu m after the extraction and heat setting of the film. The film had puncture strength (N/ mu m) of 0.21, permeability (10-5 Darcy) of 3.5, and melt fracture temperature ( degrees C) of 179 degrees C.