Wavelength tunable vertical-cavity surface-emitting lasers (VCSEL's) are potentially useful for future optical communications. Traditionally, the emission wavelength of a vertical cavity laser was turned by modulating the active region temperature, However, thermal tuning is slow, and the realized tuning range is quite limited. Micromachined tunable VCSEL's (Mi-T-VCSEL's) combine the traditional vertical cavity lases structure with a monolithically micromachined deformable membrane, enabling continuous wavelength tuning without mode !topping, In addition to a large wavelength tuning range, this technique does not suffer from the shortcomings of the thermal tuning technique, This paper presents the background theory, processing sequence, and experimental results for Mi-T-VCSEL's.