This paper presents new organic vapor sensitive device using anodized porous silicon (PS). The sensor has aluminum (Al)/PS/p-Si/Al Schottky diode structure and sensitivity at room temperature in 2600 ppm acetone, methanol, 2-propanol and ethanol is about 4, 5, 10 and 40 times respectively. The sensitivity in 800–2600 ppm ethanol vapor is 2 to 40 times. The diode sensor can be converted into an Al/PS/Al resistor sensor by switching the electrical contacts, and the sensitivity is about 500 times for a humidity change of 43–75%. All sensors have response time of about 0.5 min. The sensitivity is stable with time and the PS sensor can be integrated into VLSI Si devices to form novel microelectronic systems.