Patent ID: 6972232

Claim:
A method of manufacturing a P-channel MOSFET, comprising: forming a trench within an N-type semiconductor substrate; forming a gate oxide film on an inner surface of the trench; depositing a first polycrystalline silicon film on the semiconductor substrate; implanting BF 2 ions into the first polycrystalline silicon film by utilizing an ion implantation method and carrying out a first heat treatment; depositing a second polycrystalline silicon film on the heated first polycrystalline silicon film; implanting BF 2 ions into the second polycrystalline silicon film by utilizing the ion implantation method and carrying out a second heat treatment; depositing a third polycrystalline silicon on the second polycrystalline silicon film; and implanting BF 2 ions into the third polycrystalline silicon film by utilizing the ion implantation method and carrying out a third heat treatment.