An 0.18-μm CMOS technology with multi-Vth 's for mixed high-speed digital and RF-analog applications has been developed. The Vth 's of MOSFET's for digital circuits are 0.4 V for NMOS and -0.4 V for PMOS, respectively. In addition, there are n-MOSFET's with zero-volt-Vth for RF analog circuits. The zero-volt-Vth MOSFET's were made by using undoped epitaxial layer for the channel regions. Though the epitaxial film was grown by reduced pressure chemical vapor deposition (RP-CVD) at 750 °C, the film quality is as good as the bulk silicon because high pre-heating temperature (940 °C for 30 s) is used in H2 atmosphere before the epitaxial growth. The epitaxial channel MOSFET shows higher peak gm and fT values than those of bulk cases. Furthermore, the gm and fT values of the epitaxial channel MOSFET show significantly improved performances under the lower supply voltage compared with those of bulk. This is very important for RF analog application for low supply voltage. The undoped-epitaxial-channel MOSFET's with zero-Vth will become a key to realize high-performance and low-power CMOS devices for mixed digital and RF-analog applications.