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 $2.5mm{ imes}2.5mm$, 0.5${mu}m$ thick low stress silicon nitride membrane, $2mm{ imes}2mm$ Au/Ni/Cr membrane electrode, and 3${mu}m$ thick Au/Sn layer. The backplate chip has $2mm{ imes}2mm$, 150${mu}m$ thick single crystal silicon rigid backplate, $1.8mm{ imes}1.8mm$ backplate electrode, and air gap, which is fabricated by bulk micromachining and silicon deep reactive ion etching. Slots and $50{sim}60{mu}m$ 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.