我國專利法施行細則第19條第四項規定，請求項之技術特徵得以手段功能用語或步驟功能用語撰寫，惟此種以功能取代請求項技術特徵之結構、材料或動作之功能用語撰寫方式，於說明書中應有如何的支持，方能滿足專利法第26條第二項的請求項明確性要件，專利法與專利法施行細則均無規定。相較於我國法院判決認為，功能用語請求項與說明書中的內容，以該發明領域具有通常知識者可以理解並可據以實施即為已足，美國法院有不同之處理。在美國法院的解釋下，雖美國專利法第112條第(f)項明訂申請人得以功能用語界定專利請求項，但仍不得違反第112條第(b)項的請求項明確性義務，即申請人應特別指出與清楚說明其發明，使公眾得以理解其請求項的權利範圍，故美國法院認為縱使申請人得依第112條第(f)項以功能用語界定專利，但為符合第112條第(b)項的請求項明確性規定，使PHOSITA得以瞭解請求項確切的權利範圍，說明書中仍應撰寫對應該功能的結構、材料或動作，以防止專利申請人欲以功能用語將所有得達成該功能的技術納入專利權利範圍，而有害公益。本文認為美國基於防止專利申請人濫用功能用語之撰寫方式，將所有能達成所稱功能之結構、材料或動作納入請求項中而妨害專利之公示效果，要求申請人須於說明書中撰寫對應該功能的結構、材料或動作之解釋，應較符合明確性要件之法理，建議我國未來無論於立法或司法機關，應採納此一見解以解決手段功能用語或步驟功能用語之明確性問題。另外，本文亦主張手段功能用語與步驟功能用語係分別用以撰寫物之發明與方法發明，前者應於說明書中對應有形之結構、材料，後者應於說明書中對應無形之動作、流程，二者不得互換，否則該請求項即不明確。

Article 19(4) of Taiwan’s Enforcement Rules of the Patent Act permits means-plus-function and steps-plus-function claims. However, without recit-ing the structure, material or acts performing the claimed function, claims may face challenges about the definiteness requirement. One of the related debates is whether the specification should recite the corresponding structure, material or acts of the claimed function. This issue has been brought up both in Taiwan and U.S. jurisdictions. This study compares Taiwan court decisions with the U.S. decisions which touch on the definiteness of means-plus-function and steps-plus-function claims. We find that while the U.S. courts require that the specification has to recite the corresponding structure, material or acts of means-plus-function and steps-plus-function claims to satisfy the definiteness requirement, Taiwan courts do not adopt the same standard. This study argues that by requiring specifications disclose the corresponding structure, material or acts implementing claimed function to satisfy the definiteness requirement, the standard made by U.S. court decisions limits the metes and bounds of means-plus-function and steps-plus-function claims to a more reasonable ex-tent in order to prevent the abuse of functional claims. This study further sug-gests that Taiwan’s legislative and judicial branches of the government should adopt the same standard to prevent future definiteness disputes. Additionally, this study contends that means-plus-function can be used for device claims while steps-plus-function can be used for method claims. Due to this distinc-tion, this study concludes that the corresponding disclosure of means-plus-function claims in the specification should be structures or materials which have concrete forms, while the corresponding disclosure of steps-plus-function claims in the specification should be acts which should have no con-crete forms.