surface of the mounting table 101 so that the substrate w can be electrostatically chucked onto the mounting table 101 a shower plate 111 is attached at the top opening of the processing chamber 100 through a sealing member 110 such as an 0 ring for securing an airtight seal the shower plate 111 is formed of e g a dielectric material such as al 2 o 3 or the like the top opening of the processing chamber 100 is closed by the shower plate 111 a rlsa 113 for supplying a microwave to generate plasma is provided at the upper side of the shower plate 111 with a cover plate 112 interposed therebetween the shower plate 111 is formed e g in a disk shape and disposed so as to face the mounting table 101 at the shower plate 111 a plurality of gas supply openings 114 are formed to extend vertically therethrough a gas supply line 115 is horizontally extended through the shower plate 111 to the middle portion thereof from the side surface of the processing chamber 100 and is opened at the top surface of the shower plate 111 by a recess formed in the top surface of the shower plate 111 a gas channel 116 is formed between the shower plate 111 and the cover plate 112 the gas channel 116 is in communication with the gas supply line 115 and each of the gas supply openings 114 accordingly the plasma gas supplied to the gas supply line 115 is delivered to the gas channel 116 through the gas supply line 115 and is supplied into the processing chamber 100 through.