Doubt regarding on the Thin Film Resistor(TFR) in ADS

I am using Microstrip Thin Film Resistor (TFR) to my work. In the TFR, we can change Width , Length , Sheet resistivity( Rs) as our wish.
What is my doubt, is this TFR with desired W, L, and Rs available in the market. As we know SMT Resistors Width and Lengths are fixed case styles 0805,0603 are available in the Market. But in case of microstrip TFR , we can change W,L, and Rs. Is this W,L, and Rs available in the market.

For SMD, we usually use library elements from the SMD manufacturer, not the TFR model.

The TFR model is typically used for thin film (hybrid) technology, where the Rs is defined by the technology and you set W and L as needed.

TFRs are not manufactured parts bought from a catalog. Rather they are manufactured directly as part of the board or laminate being produced. You can make then any size required according to the material being used to make it.

Suppose I use RT/duroid 5880 , their Height =0.508mm, T=0.035mm, Er= 2.20, Tand=0.009, Can I change TFR W,L and Rs as my requirement. How it TFR will get the Rs(Sheet resistivity). Once we define the MSUB electrical (H,T,TadD, Er)parameters, automatically those MSUB paramaeters will apply for TFR as like Simple Microstrip line(MLIN). Can you clear this doubt.

As Volker said in his post TFRs are for thin film (hybrid) technology. This is a additive process where conductor and resistor material is added to a substrate, often a ceramic tile. The differenct properties of the final circuit are thus set by the material being added.

RT/Duriod is used for etch processes which are subtractive. Copper is removed to create the required interconnect structors. There is no resistive material to make resistors. I do not know of any way to create TFRs on RT/Duriod. You would have to use surface mount components for that application.

Normal RT/duroid 5880 has only the copper metalization, and no additional resistive layer. Adding sheet resistors is standard in thin film hybrid technology (printed onto the ceramic substrate) but very exotic if you work with RT/duroid 5880 or other PCB materials.

There is a resistive sheet option listed by Rogers here (at the bottom of the table)
http://www.rogerscorp.com/documents/...-Materials.pdf
and mentioned here:
http://www.rogerscorp.com/documents/...oard-Space.pdf
But this is really exotic.

The sheet resistance Rs is a material property of that extra resistor foil.