IoCreateDevice for creating RAM Drive

Hi,

I want to create 3 different types of Device. For that I have used "IoCreateDevice" function and for changing device characteristics I did the as following

1) For Fixed drive type

IoCreateDevice(
DriverObject,
sizeof(DEVICE_EXTENSION),
&uniDeviceName,
FILE_DEVICE_DISK ,
(FILE_DEVICE_SECURE_OPEN),
FALSE, // This isn't an exclusive device
&functionDeviceObject
);

2) Removable drive type

IoCreateDevice(
DriverObject,
sizeof(DEVICE_EXTENSION),
&uniDeviceName,
FILE_DEVICE_DISK ,
FILE_REMOVABLE_MEDIA,
FALSE, // This isn't an exclusive device
&functionDeviceObject
);

3) Ram drive type: There is not any define value as "FILE_REMOVABLE_MEDIA" for RAM Drive type. So how can I set this value.

Could anybody tell me what value should I use at device characteristics field for creating a device as RAM Drive type?

Thanks in advance,

Imran