This paper presents a novel MEMS condenser microphone with rigid backplate to enhance acoustic characteristics. The MEMS condenser microphone consists of membrane and backplate chips which are bonded together by gold-tin (Au/Sn) eutectic solder bonding. The membrane chip has 2.5 mm${ imes}$2.5 mm, $0.5{mu}m$ thick low stress silicon nitride membrane, 2 mm${ imes}$2 mm Au/Ni/Cr membrane electrode, and $3{mu}m$ thick Au/Sn layer. The backplate chip has 2 mm${ imes}$2 mm, $150{mu}m$ thick single crystal silicon rigid backplate, 1.8 mm${ imes}$1.8 mm backplate electrode, and air gap, which is fabricated by bulk micromachining and silicon deep reactive ion etching. Slots and $50-60{mu}m$ radius circular acoustic holes to reduce air damping are also formed in the backplate chip. The fabricated microphone sensitivity is $39.8{mu}V/Pa$ (-88 dB re. 1 V/Pa) at 1 kHz and 28 V polarization voltage. The microphone shows flat frequency response within 1 dB between 20 Hz and 5 kHz.