Direct bonding of single crystalline quartz wafers is presented. By this straightforward technique, hermetical seals between quartz wafers can be formed. Nearly Z-cut (the Z-cut rotated 1 degrees 50＇) and AT-cut wafers bonded spontaneously at room temperature after wet chemical cleaning. The bond strength, measured by the crack opening method, increased with the annealing temperature up to 400 degrees C. After annealing at 500 degrees C, the wafers shattered when the blade was inserted, indicating an even stronger bond. Z-cut wafers bonded spontaneously at room temperature only after additional chemical mechanical polishing and wet chemical cleaning. Hermetically sealed cavities were made using direct bonding over etched pits. The combination of direct bonding with wet chemical etching of quartz demonstrates the usefulness for micromechanical purposes, as more complex three-dimensional structures can be formed.