| 摘要 |
PURPOSE:To reduce the cost by thermally oxidizing a gate electrode having an impurity-doped polycrystalline silicon layer to form an oxide film side wall on the side of the layer, thereby simplifying the process. CONSTITUTION:A field silicon oxide film 2 is formed on the main surface of a P type silicon substrate 1, and an SiO2 film 3 is formed as a gate insulating film on an element forming region. A polycrystalline silicon layer 4 is formed, and phosphorus is doped. A gate electrode 5 is formed by etching, phosphorus ions are implanted on the overall surface, and a low density N type ion implanted layer 6 is formed on the source and drain forming regions implanted with the phosphorus on the overall surface. A gate electrode 5 is thermally oxidized to form thickly a thermally oxidized film 11 on the overall surface. The films 11 at both sides of the layer 4 are utilized as oxide film side walls 11a. A high density phosphorus or arsenic ion implanted layer 8 is formed, annealed to form a source region 9 and a drain region 10. Side wall forming steps become unnecessary, and MOSFET can be formed in a simple process in a structure for alleviating a drain electric field. |
