A method sterilizes a device having a diffusion restricted area and a non-diffusion restricted area. The method includes the steps of contacting the device with liquid sterilant outside or inside a sterilization chamber fluidly connected to at least one pump, placing the device in the chamber (before or after the contacting step), bringing the pressure of the chamber to a first pressure range at which liquid sterilant is vaporized from the non-diffusion restricted area to sterilize the non-diffusion restricted area, and bringing the pressure of the chamber to a second pressure range at which the liquid sterilant is vaporized from the diffusion restricted area to sterilize the diffusion restricted area. The minimum pressure in the second pressure range is lower than the maximum pressure in the first pressure range.