In order to reduce power dissipation requirements, obtain full potential transistor performance and avoid power dissipation limitations on transistor performance in high density integrated circuits, transistors are operated in a sub-threshold (sub-Vth) or a near sub-Vth voltage regime (generally about 0.2 volts rather than a super-Vth regime of about 1.2 volts or higher) and optimized for such operation, particularly through simplification of the transistor structure, since intrinsic channel resistance is dominant in sub-Vth operating voltage regimes. Such simplifications include an underlap or recess of the source and drain regions from the gate which avoids overlap capacitance to partially recover loss of switching speed otherwise caused by low voltage operation, an ultra-thin gate structure having a thickness of 500 Å or less which also simplifies forming connections to the transistor and an avoidance of silicidation or alloy formation in the source, drain and/or gate of transistors.