The goal of dissertation is to explore feasibility of designing millimeter-wave (mmWave) circuits in CMOS technology, especially when frequency is close to the maximum oscillation frequency f[subscript max] of the active device. In this dissertation, an embedding network method is proposed to design high efficiency fundamental oscillators and high gain amplifier. First, it reports an approach to designing compact high efficiency mmWave fundamental oscillators operating above the f[subscript max]/2 of the active device. The approach takes full consideration of the nonlinearity of the active device and the finite quality factor of the passive devices to provide an accurate and optimal oscillator design in terms of the output power and efficiency. 213-GHz single-ended and differential fundamental oscillators in 65-nm CMOS technology are presented to demonstrate the effectiveness of the proposed method. Using a compact capacitive transformer design, the single-ended oscillator achieves 0.79-mW output power per transistor (16 [mu]m) at 1.0-V supply and a peak dc-to-RF efficiency of 8.02% (V[subscript DD]=0.80 V) within a core area of 0.0101 mm2, and the measured phase noise is −93.4 dBc/Hz at 1-MHz offset. The differential oscillator exhibits approximately the same performance. A 213-GHz fundamental voltage-controlled oscillator (VCO) with bulk tuning method is also developed in this work. The measured peak efficiency of the VCO is 6.02% with a tuning rang of 2.3% at 0.6-V supply.In order to further improve dc-to-RF efficiency, an optimization-based design methodology is then proposed for high-power and high-efficiency mmWave fundamental oscillators in CMOS technology. The optimization is formulated to take into account the loss of the passive components to result in an optimal circuit design. The proposed approach can produce the final design in a single pass of optimization with a fast and robust convergence profile. A comparative study between the T - and the [pi]-embedding networks is presented. It shows that T -embedding is superior to [pi]-embedding in terms of flexibility in biasing and sensitivity to component Q. A design example of a 215-GHz fundamental oscillator in a 65-nm CMOS technology is presented to demonstrate the effectiveness of the proposed design approach. The oscillator achieves 5.17-dBm peak output power at 1.2-V supply with a corresponding dc-to-RF efficiency 12.3% and a peak efficiency of 13.7%. The measured phase noise is −90.0 dBc/Hz and −116.2 dBc/Hz at 1 MHz and 10 MHz offset, respectively. Lastly, embedding network theory is presented to design high gain amplifier in this dissertation. Two embedding theories, constant GC/U and G[subscript max]/GC, are proposed. A 210-GHz high gain amplifier example is designed. Two 16 [mu]m NMOS transistors consist of a differential circuit with V[subscript DD] = 1.2 V and VG = 0.45 V. The total dc power of the designed 210-GHz amplifier is 12.8 mW. The simulated Gain S21 is 16.66 dB. NF is 7.38 dB. Stability factor k is 3.82 at 210 GHz. The simulated 1dB compression point P1dB, input referred third-order intercept point, IIP3 is -22.33 dB, and -12.97 dB, respectively. These simulated results demonstrate the effectiveness of the proposed design theory.